21991232 has 56 divisors (see below), whose sum is σ = 45732192. Its totient is φ = 10483200.

The previous prime is 21991231. The next prime is 21991267. The reversal of 21991232 is 23219912.

It is a super-2 number, since 2×21991232² = 967228569755648, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21991195 and 21991204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991231) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 167807 + ... + 167937.

Almost surely, 2^21991232 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 21991232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22866096).

21991232 is an abundant number, since it is smaller than the sum of its proper divisors (23740960).

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

21991232 is a wasteful number, since it uses less digits than its factorization.

21991232 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 237 counting only the distinct ones).

The product of its digits is 1944, while the sum is 29.

The square root of 21991232 is about 4689.4809947371. The cubic root of 21991232 is about 280.1667034512.

The spelling of 21991232 in words is "twenty-one million, nine hundred ninety-one thousand, two hundred thirty-two".