21913651 has 4 divisors (see below), whose sum is σ = 22213912. Its totient is φ = 21613392.

The previous prime is 21913643. The next prime is 21913679. The reversal of 21913651 is 15631912.

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 21913651 - 2³ = 21913643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21913601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 150021 + ... + 150166.

It is an arithmetic number, because the mean of its divisors is an integer number (5553478).

Almost surely, 2^21913651 is an apocalyptic number.

21913651 is a deficient number, since it is larger than the sum of its proper divisors (300261).

21913651 is an equidigital number, since it uses as much as digits as its factorization.

21913651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300260.

The product of its digits is 1620, while the sum is 28.

The square root of 21913651 is about 4681.2018755871. The cubic root of 21913651 is about 279.8368564926.

The spelling of 21913651 in words is "twenty-one million, nine hundred thirteen thousand, six hundred fifty-one".