21981232 has 80 divisors (see below), whose sum is σ = 54218752. Its totient is φ = 8398080.

The previous prime is 21981229. The next prime is 21981251. The reversal of 21981232 is 23218912.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a self number, because there is not a number n which added to its sum of digits gives 21981232.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 44893 + ... + 45379.

Almost surely, 2^21981232 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 21981232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27109376).

21981232 is an abundant number, since it is smaller than the sum of its proper divisors (32237520).

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

21981232 is a wasteful number, since it uses less digits than its factorization.

21981232 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546 (or 540 counting only the distinct ones).

The product of its digits is 1728, while the sum is 28.

The square root of 21981232 is about 4688.4146574295. The cubic root of 21981232 is about 280.1242305874.

The spelling of 21981232 in words is "twenty-one million, nine hundred eighty-one thousand, two hundred thirty-two".