20209931 has 4 divisors (see below), whose sum is σ = 23097072. Its totient is φ = 17322792.

The previous prime is 20209909. The next prime is 20209933. The reversal of 20209931 is 13990202.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13990202 = 2 ⋅6995101.

It is a cyclic number.

It is not a de Polignac number, because 20209931 - 2¹⁰ = 20208907 is a prime.

It is a super-2 number, since 2×20209931² = 816882622049522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20209931.

It is not an unprimeable number, because it can be changed into a prime (20209933) 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, 1443560 + ... + 1443573.

It is an arithmetic number, because the mean of its divisors is an integer number (5774268).

Almost surely, 2^20209931 is an apocalyptic number.

20209931 is a deficient number, since it is larger than the sum of its proper divisors (2887141).

20209931 is an equidigital number, since it uses as much as digits as its factorization.

20209931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2887140.

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 20209931 is about 4495.5456843413. The cubic root of 20209931 is about 272.3881919335.

The spelling of 20209931 in words is "twenty million, two hundred nine thousand, nine hundred thirty-one".