20187979 has 4 divisors (see below), whose sum is σ = 23071984. Its totient is φ = 17303976.

The previous prime is 20187961. The next prime is 20187983. The reversal of 20187979 is 97978102.

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: 97978102 = 2 ⋅48989051.

It is a cyclic number.

It is not a de Polignac number, because 20187979 - 2⁹ = 20187467 is a prime.

It is a super-2 number, since 2×20187979² = 815108992208882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20187989) 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, 1441992 + ... + 1442005.

It is an arithmetic number, because the mean of its divisors is an integer number (5767996).

Almost surely, 2^20187979 is an apocalyptic number.

20187979 is a deficient number, since it is larger than the sum of its proper divisors (2884005).

20187979 is an equidigital number, since it uses as much as digits as its factorization.

20187979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2884004.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20187979 is about 4493.1034931326. The cubic root of 20187979 is about 272.2895336409.

The spelling of 20187979 in words is "twenty million, one hundred eighty-seven thousand, nine hundred seventy-nine".