21991876 has 6 divisors (see below), whose sum is σ = 38485790. Its totient is φ = 10995936.

The previous prime is 21991847. The next prime is 21991883. The reversal of 21991876 is 67819912.

It can be written as a sum of positive squares in only one way, i.e., 15366400 + 6625476 = 3920^2 + 2574^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2748981 + ... + 2748988.

Almost surely, 2^21991876 is an apocalyptic number.

It is an amenable number.

21991876 is a deficient number, since it is larger than the sum of its proper divisors (16493914).

21991876 is a wasteful number, since it uses less digits than its factorization.

21991876 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5497973 (or 5497971 counting only the distinct ones).

The product of its digits is 54432, while the sum is 43.

The square root of 21991876 is about 4689.5496585493. The cubic root of 21991876 is about 280.1694382623.

The spelling of 21991876 in words is "twenty-one million, nine hundred ninety-one thousand, eight hundred seventy-six".