21397992 has 64 divisors (see below), whose sum is σ = 66700800. Its totient is φ = 5557440.

The previous prime is 21397949. The next prime is 21397997. The reversal of 21397992 is 29979312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is not an unprimeable number, because it can be changed into a prime (21397997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3942 + ... + 7637.

It is an arithmetic number, because the mean of its divisors is an integer number (1042200).

Almost surely, 2^21397992 is an apocalyptic number.

21397992 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21397992 is an abundant number, since it is smaller than the sum of its proper divisors (45302808).

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

21397992 is a wasteful number, since it uses less digits than its factorization.

21397992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11606 (or 11602 counting only the distinct ones).

The product of its digits is 61236, while the sum is 42.

The square root of 21397992 is about 4625.7963638708. The cubic root of 21397992 is about 277.6244259804.

The spelling of 21397992 in words is "twenty-one million, three hundred ninety-seven thousand, nine hundred ninety-two".