21437651 has 4 divisors (see below), whose sum is σ = 21467400. Its totient is φ = 21407904.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437651 is 15673412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21437651 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21437851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13766 + ... + 15243.

It is an arithmetic number, because the mean of its divisors is an integer number (5366850).

Almost surely, 2^21437651 is an apocalyptic number.

21437651 is a deficient number, since it is larger than the sum of its proper divisors (29749).

21437651 is an equidigital number, since it uses as much as digits as its factorization.

21437651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29748.

The product of its digits is 5040, while the sum is 29.

The square root of 21437651 is about 4630.0811008016. The cubic root of 21437651 is about 277.7958363312.

The spelling of 21437651 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred fifty-one".