231021520 has 40 divisors (see below), whose sum is σ = 540757800. Its totient is φ = 91783680.

The previous prime is 231021493. The next prime is 231021523. The reversal of 231021520 is 25120132.

231021520 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 14107536 + 216913984 = 3756^2 + 14728^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×231021520² = 106741885406220800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 231021494 and 231021503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231021523) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2230 + ... + 21610.

It is an arithmetic number, because the mean of its divisors is an integer number (13518945).

Almost surely, 2^231021520 is an apocalyptic number.

231021520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 231021520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (270378900).

231021520 is an abundant number, since it is smaller than the sum of its proper divisors (309736280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

231021520 is a wasteful number, since it uses less digits than its factorization.

231021520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19543 (or 19537 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 231021520 is about 15199.3920931069. The cubic root of 231021520 is about 613.5982970907.

Adding to 231021520 its reverse (25120132), we get a palindrome (256141652).

The spelling of 231021520 in words is "two hundred thirty-one million, twenty-one thousand, five hundred twenty".