21808868 has 6 divisors (see below), whose sum is σ = 38165526. Its totient is φ = 10904432.

The previous prime is 21808867. The next prime is 21808879. The reversal of 21808868 is 86880812.

It can be written as a sum of positive squares in only one way, i.e., 12124324 + 9684544 = 3482^2 + 3112^2 .

It is not an unprimeable number, because it can be changed into a prime (21808861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2726105 + ... + 2726112.

It is an arithmetic number, because the mean of its divisors is an integer number (6360921).

Almost surely, 2^21808868 is an apocalyptic number.

It is an amenable number.

21808868 is a deficient number, since it is larger than the sum of its proper divisors (16356658).

21808868 is a wasteful number, since it uses less digits than its factorization.

21808868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5452221 (or 5452219 counting only the distinct ones).

The product of its (nonzero) digits is 49152, while the sum is 41.

The square root of 21808868 is about 4669.9965738745. The cubic root of 21808868 is about 279.3901181288.

The spelling of 21808868 in words is "twenty-one million, eight hundred eight thousand, eight hundred sixty-eight".