21662651 has 4 divisors (see below), whose sum is σ = 21873072. Its totient is φ = 21452232.

The previous prime is 21662633. The next prime is 21662653. The reversal of 21662651 is 15626612.

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

It is a cyclic number.

It is not a de Polignac number, because 21662651 - 2¹⁸ = 21400507 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21662653) 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, 105056 + ... + 105261.

It is an arithmetic number, because the mean of its divisors is an integer number (5468268).

Almost surely, 2^21662651 is an apocalyptic number.

21662651 is a deficient number, since it is larger than the sum of its proper divisors (210421).

21662651 is a wasteful number, since it uses less digits than its factorization.

21662651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210420.

The product of its digits is 4320, while the sum is 29.

The square root of 21662651 is about 4654.3153094736. The cubic root of 21662651 is about 278.7643295334.

The spelling of 21662651 in words is "twenty-one million, six hundred sixty-two thousand, six hundred fifty-one".