21533988 has 48 divisors (see below), whose sum is σ = 57697920. Its totient is φ = 6123264.

The previous prime is 21533987. The next prime is 21533999. The reversal of 21533988 is 88933512.

It is not an unprimeable number, because it can be changed into a prime (21533983) 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, 22120 + ... + 23072.

It is an arithmetic number, because the mean of its divisors is an integer number (1202040).

Almost surely, 2^21533988 is an apocalyptic number.

21533988 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21533988 is an abundant number, since it is smaller than the sum of its proper divisors (36163932).

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

21533988 is a wasteful number, since it uses less digits than its factorization.

21533988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1236 (or 1234 counting only the distinct ones).

The product of its digits is 51840, while the sum is 39.

The square root of 21533988 is about 4640.4728207371. The cubic root of 21533988 is about 278.2113362904.

The spelling of 21533988 in words is "twenty-one million, five hundred thirty-three thousand, nine hundred eighty-eight".