21531400 has 48 divisors (see below), whose sum is σ = 54617040. Its totient is φ = 7828800.

The previous prime is 21531379. The next prime is 21531439. The reversal of 21531400 is 413512.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2694 + ... + 7093.

It is an arithmetic number, because the mean of its divisors is an integer number (1137855).

Almost surely, 2^21531400 is an apocalyptic number.

21531400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531400 is an abundant number, since it is smaller than the sum of its proper divisors (33085640).

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

21531400 is a wasteful number, since it uses less digits than its factorization.

21531400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9814 (or 9805 counting only the distinct ones).

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

The square root of 21531400 is about 4640.1939614632. The cubic root of 21531400 is about 278.2001905025.

Adding to 21531400 its reverse (413512), we get a palindrome (21944912).

It can be divided in two parts, 2153 and 1400, that added together give a palindrome (3553).

The spelling of 21531400 in words is "twenty-one million, five hundred thirty-one thousand, four hundred".