21021679 has 8 divisors (see below), whose sum is σ = 24082560. Its totient is φ = 17975256.

The previous prime is 21021667. The next prime is 21021683. The reversal of 21021679 is 97612012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21021679 - 2⁵ = 21021647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021629) 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 7 ways as a sum of consecutive naturals, for example, 289 + ... + 6490.

It is an arithmetic number, because the mean of its divisors is an integer number (3010320).

Almost surely, 2^21021679 is an apocalyptic number.

21021679 is a deficient number, since it is larger than the sum of its proper divisors (3060881).

21021679 is an equidigital number, since it uses as much as digits as its factorization.

21021679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7229.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21021679 is about 4584.9404576286. The cubic root of 21021679 is about 275.9873226341.

The spelling of 21021679 in words is "twenty-one million, twenty-one thousand, six hundred seventy-nine".