16721979 has 4 divisors (see below), whose sum is σ = 22295976. Its totient is φ = 11147984.

The previous prime is 16721953. The next prime is 16721981. The reversal of 16721979 is 97912761.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97912761 = 3 ⋅32637587.

It is a cyclic number.

It is not a de Polignac number, because 16721979 - 2⁸ = 16721723 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 16721979.

It is not an unprimeable number, because it can be changed into a prime (16721279) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2786994 + ... + 2786999.

It is an arithmetic number, because the mean of its divisors is an integer number (5573994).

Almost surely, 2^16721979 is an apocalyptic number.

16721979 is a deficient number, since it is larger than the sum of its proper divisors (5573997).

16721979 is an equidigital number, since it uses as much as digits as its factorization.

16721979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5573996.

The product of its digits is 47628, while the sum is 42.

The square root of 16721979 is about 4089.2516430271. The cubic root of 16721979 is about 255.7187411929.

The spelling of 16721979 in words is "sixteen million, seven hundred twenty-one thousand, nine hundred seventy-nine".