21173979 has 8 divisors (see below), whose sum is σ = 28710720. Its totient is φ = 13876616.

The previous prime is 21173969. The next prime is 21173983. The reversal of 21173979 is 97937112.

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 21173979 - 2⁴ = 21173963 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21173939) 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, 59637 + ... + 59990.

It is an arithmetic number, because the mean of its divisors is an integer number (3588840).

Almost surely, 2^21173979 is an apocalyptic number.

21173979 is a deficient number, since it is larger than the sum of its proper divisors (7536741).

21173979 is a wasteful number, since it uses less digits than its factorization.

21173979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119689.

The product of its digits is 23814, while the sum is 39.

The square root of 21173979 is about 4601.5192056537. The cubic root of 21173979 is about 276.6522198550.

The spelling of 21173979 in words is "twenty-one million, one hundred seventy-three thousand, nine hundred seventy-nine".