21531120 has 160 divisors (see below), whose sum is σ = 73661952. Its totient is φ = 5170176.

The previous prime is 21531119. The next prime is 21531121. The reversal of 21531120 is 2113512.

It is an interprime number because it is at equal distance from previous prime (21531119) and next prime (21531121).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21531120.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531121) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 208989 + ... + 209091.

Almost surely, 2^21531120 is an apocalyptic number.

21531120 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 21531120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36830976).

21531120 is an abundant number, since it is smaller than the sum of its proper divisors (52130832).

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

21531120 is a wasteful number, since it uses less digits than its factorization.

21531120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199 (or 193 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21531120 is about 4640.1637902126. The cubic root of 21531120 is about 278.1989845678.

Adding to 21531120 its reverse (2113512), we get a palindrome (23644632).

The spelling of 21531120 in words is "twenty-one million, five hundred thirty-one thousand, one hundred twenty".