21920784 has 20 divisors (see below), whose sum is σ = 56628816. Its totient is φ = 7306912.

The previous prime is 21920749. The next prime is 21920791. The reversal of 21920784 is 48702912.

It is a happy number.

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 3 ways as a sum of consecutive naturals, for example, 228294 + ... + 228389.

Almost surely, 2^21920784 is an apocalyptic number.

21920784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21920784 is an abundant number, since it is smaller than the sum of its proper divisors (34708032).

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

21920784 is a wasteful number, since it uses less digits than its factorization.

21920784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 456694 (or 456688 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21920784 is about 4681.9636905897. The cubic root of 21920784 is about 279.8672159515.

The spelling of 21920784 in words is "twenty-one million, nine hundred twenty thousand, seven hundred eighty-four".