21415979 has 4 divisors (see below), whose sum is σ = 23063376. Its totient is φ = 19768584.

The previous prime is 21415969. The next prime is 21415987. The reversal of 21415979 is 97951412.

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 21415979 - 2¹² = 21411883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21415969) 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, 823679 + ... + 823704.

It is an arithmetic number, because the mean of its divisors is an integer number (5765844).

Almost surely, 2^21415979 is an apocalyptic number.

21415979 is a deficient number, since it is larger than the sum of its proper divisors (1647397).

21415979 is a wasteful number, since it uses less digits than its factorization.

21415979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1647396.

The product of its digits is 22680, while the sum is 38.

The square root of 21415979 is about 4627.7401612450. The cubic root of 21415979 is about 277.7021939005.

The spelling of 21415979 in words is "twenty-one million, four hundred fifteen thousand, nine hundred seventy-nine".