21991874 has 4 divisors (see below), whose sum is σ = 32987814. Its totient is φ = 10995936.

The previous prime is 21991847. The next prime is 21991883. The reversal of 21991874 is 47819912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 11055625 + 10936249 = 3325^2 + 3307^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5497967 + ... + 5497970.

Almost surely, 2^21991874 is an apocalyptic number.

21991874 is a deficient number, since it is larger than the sum of its proper divisors (10995940).

21991874 is a wasteful number, since it uses less digits than its factorization.

21991874 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10995939.

The product of its digits is 36288, while the sum is 41.

The square root of 21991874 is about 4689.5494453092. The cubic root of 21991874 is about 280.1694297692.

The spelling of 21991874 in words is "twenty-one million, nine hundred ninety-one thousand, eight hundred seventy-four".