21012372 has 30 divisors (see below), whose sum is σ = 54931338. Its totient is φ = 7004016.

The previous prime is 21012371. The next prime is 21012373. The reversal of 21012372 is 27321012.

It is an interprime number because it is at equal distance from previous prime (21012371) and next prime (21012373).

It can be written as a sum of positive squares in only one way, i.e., 19766916 + 1245456 = 4446^2 + 1116^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 32103 + ... + 32750.

Almost surely, 2^21012372 is an apocalyptic number.

It is an amenable number.

21012372 is an abundant number, since it is smaller than the sum of its proper divisors (33918966).

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

21012372 is a wasteful number, since it uses less digits than its factorization.

21012372 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64869 (or 64858 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21012372 is about 4583.9253920630. The cubic root of 21012372 is about 275.9465870174.

Adding to 21012372 its reverse (27321012), we get a palindrome (48333384).

The spelling of 21012372 in words is "twenty-one million, twelve thousand, three hundred seventy-two".