21675651 has 4 divisors (see below), whose sum is σ = 28900872. Its totient is φ = 14450432.

The previous prime is 21675649. The next prime is 21675659. The reversal of 21675651 is 15657612.

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 21675651 - 2¹ = 21675649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21675659) 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, 3612606 + ... + 3612611.

It is an arithmetic number, because the mean of its divisors is an integer number (7225218).

Almost surely, 2^21675651 is an apocalyptic number.

21675651 is a deficient number, since it is larger than the sum of its proper divisors (7225221).

21675651 is an equidigital number, since it uses as much as digits as its factorization.

21675651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7225220.

The product of its digits is 12600, while the sum is 33.

The square root of 21675651 is about 4655.7116534425. The cubic root of 21675651 is about 278.8200815834.

The spelling of 21675651 in words is "twenty-one million, six hundred seventy-five thousand, six hundred fifty-one".