21457764 has 48 divisors (see below), whose sum is σ = 58564800. Its totient is φ = 6775488.

The previous prime is 21457759. The next prime is 21457771. The reversal of 21457764 is 46775412.

21457764 is a `hidden beast` number, since 21 + 4 + 577 + 64 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3177 + ... + 7280.

It is an arithmetic number, because the mean of its divisors is an integer number (1220100).

Almost surely, 2^21457764 is an apocalyptic number.

It is an amenable number.

21457764 is an abundant number, since it is smaller than the sum of its proper divisors (37107036).

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

21457764 is a wasteful number, since it uses less digits than its factorization.

21457764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10489 (or 10481 counting only the distinct ones).

The product of its digits is 47040, while the sum is 36.

The square root of 21457764 is about 4632.2525837869. The cubic root of 21457764 is about 277.8826860395.

The spelling of 21457764 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred sixty-four".