21775668 has 12 divisors (see below), whose sum is σ = 50809920. Its totient is φ = 7258552.

The previous prime is 21775667. The next prime is 21775703. The reversal of 21775668 is 86657712.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21775667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 907308 + ... + 907331.

It is an arithmetic number, because the mean of its divisors is an integer number (4234160).

Almost surely, 2^21775668 is an apocalyptic number.

It is an amenable number.

21775668 is an abundant number, since it is smaller than the sum of its proper divisors (29034252).

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

21775668 is a wasteful number, since it uses less digits than its factorization.

21775668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1814646 (or 1814644 counting only the distinct ones).

The product of its digits is 141120, while the sum is 42.

The square root of 21775668 is about 4666.4406135726. The cubic root of 21775668 is about 279.2482727293.

It can be divided in two parts, 2 and 1775668, that added together give a triangular number (1775670 = T₁₈₈₄).

The spelling of 21775668 in words is "twenty-one million, seven hundred seventy-five thousand, six hundred sixty-eight".