21991626 has 24 divisors (see below), whose sum is σ = 50157120. Its totient is φ = 6944616.

The previous prime is 21991589. The next prime is 21991631. The reversal of 21991626 is 62619912.

21991626 is a `hidden beast` number, since 21 + 9 + 9 + 1 + 626 = 666.

It is a super-2 number, since 2×21991626² = 967263228247752, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31810 + ... + 32493.

It is an arithmetic number, because the mean of its divisors is an integer number (2089880).

Almost surely, 2^21991626 is an apocalyptic number.

21991626 is an abundant number, since it is smaller than the sum of its proper divisors (28165494).

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

21991626 is a wasteful number, since it uses less digits than its factorization.

21991626 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64330 (or 64327 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 21991626 is about 4689.5230034621. The cubic root of 21991626 is about 280.1683766184.

The spelling of 21991626 in words is "twenty-one million, nine hundred ninety-one thousand, six hundred twenty-six".