21391932 has 48 divisors (see below), whose sum is σ = 52496640. Its totient is φ = 6766848.

The previous prime is 21391921. The next prime is 21391939. The reversal of 21391932 is 23919312.

It is a happy number.

It is a super-2 number, since 2×21391932² = 915229509385248, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21391932.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391939) 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, 49188 + ... + 49620.

It is an arithmetic number, because the mean of its divisors is an integer number (1093680).

Almost surely, 2^21391932 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21391932, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26248320).

21391932 is an abundant number, since it is smaller than the sum of its proper divisors (31104708).

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

21391932 is a wasteful number, since it uses less digits than its factorization.

21391932 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642 (or 640 counting only the distinct ones).

The product of its digits is 2916, while the sum is 30.

The square root of 21391932 is about 4625.1412951390. The cubic root of 21391932 is about 277.5982153766.

The spelling of 21391932 in words is "twenty-one million, three hundred ninety-one thousand, nine hundred thirty-two".