21012456 has 16 divisors (see below), whose sum is σ = 52531200. Its totient is φ = 7004144.

The previous prime is 21012449. The next prime is 21012457. The reversal of 21012456 is 65421012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 437736 + ... + 437783.

It is an arithmetic number, because the mean of its divisors is an integer number (3283200).

Almost surely, 2^21012456 is an apocalyptic number.

It is an amenable number.

21012456 is an abundant number, since it is smaller than the sum of its proper divisors (31518744).

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

21012456 is a wasteful number, since it uses less digits than its factorization.

21012456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875528 (or 875524 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21012456 is about 4583.9345545066. The cubic root of 21012456 is about 275.9469547291.

Adding to 21012456 its reverse (65421012), we get a palindrome (86433468).

The spelling of 21012456 in words is "twenty-one million, twelve thousand, four hundred fifty-six".