21695651 has 4 divisors (see below), whose sum is σ = 21705600. Its totient is φ = 21685704.

The previous prime is 21695627. The next prime is 21695669. The reversal of 21695651 is 15659612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21695651 - 2¹⁰ = 21694627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21695351) 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, 131 + ... + 6588.

It is an arithmetic number, because the mean of its divisors is an integer number (5426400).

Almost surely, 2^21695651 is an apocalyptic number.

21695651 is a deficient number, since it is larger than the sum of its proper divisors (9949).

21695651 is an equidigital number, since it uses as much as digits as its factorization.

21695651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9948.

The product of its digits is 16200, while the sum is 35.

The square root of 21695651 is about 4657.8590575499. The cubic root of 21695651 is about 278.9058104566.

The spelling of 21695651 in words is "twenty-one million, six hundred ninety-five thousand, six hundred fifty-one".