20751979 has 4 divisors (see below), whose sum is σ = 20832984. Its totient is φ = 20670976.

The previous prime is 20751967. The next prime is 20752001. The reversal of 20751979 is 97915702.

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 20751979 - 2¹¹ = 20749931 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20751179) 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, 40117 + ... + 40630.

It is an arithmetic number, because the mean of its divisors is an integer number (5208246).

Almost surely, 2^20751979 is an apocalyptic number.

20751979 is a deficient number, since it is larger than the sum of its proper divisors (81005).

20751979 is an equidigital number, since it uses as much as digits as its factorization.

20751979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81004.

The product of its (nonzero) digits is 39690, while the sum is 40.

The square root of 20751979 is about 4555.4340078636. The cubic root of 20751979 is about 274.8019687240.

The spelling of 20751979 in words is "twenty million, seven hundred fifty-one thousand, nine hundred seventy-nine".