21557668 has 24 divisors (see below), whose sum is σ = 41588064. Its totient is φ = 9696000.

The previous prime is 21557651. The next prime is 21557671. The reversal of 21557668 is 86675512.

It is a self number, because there is not a number n which added to its sum of digits gives 21557668.

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 7 ways as a sum of consecutive naturals, for example, 1743 + ... + 6793.

It is an arithmetic number, because the mean of its divisors is an integer number (1732836).

Almost surely, 2^21557668 is an apocalyptic number.

It is an amenable number.

21557668 is a deficient number, since it is larger than the sum of its proper divisors (20030396).

21557668 is a wasteful number, since it uses less digits than its factorization.

21557668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5163 (or 5161 counting only the distinct ones).

The product of its digits is 100800, while the sum is 40.

The square root of 21557668 is about 4643.0235838298. The cubic root of 21557668 is about 278.3132779443.

The spelling of 21557668 in words is "twenty-one million, five hundred fifty-seven thousand, six hundred sixty-eight".