21231240 has 32 divisors (see below), whose sum is σ = 63694080. Its totient is φ = 5661632.

The previous prime is 21231173. The next prime is 21231241. The reversal of 21231240 is 4213212.

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

It is not an unprimeable number, because it can be changed into a prime (21231241) 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, 88344 + ... + 88583.

It is an arithmetic number, because the mean of its divisors is an integer number (1990440).

Almost surely, 2^21231240 is an apocalyptic number.

21231240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231240 is an abundant number, since it is smaller than the sum of its proper divisors (42462840).

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

21231240 is a wasteful number, since it uses less digits than its factorization.

21231240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176941 (or 176937 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21231240 is about 4607.7369716597. The cubic root of 21231240 is about 276.9013798290.

Adding to 21231240 its reverse (4213212), we get a palindrome (25444452).

The spelling of 21231240 in words is "twenty-one million, two hundred thirty-one thousand, two hundred forty".