20309881 has 4 divisors (see below), whose sum is σ = 20379492. Its totient is φ = 20240272.

The previous prime is 20309869. The next prime is 20309893. The reversal of 20309881 is 18890302.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (20309869) and next prime (20309893).

It can be written as a sum of positive squares in 2 ways, for example, as 15093225 + 5216656 = 3885^2 + 2284^2 .

It is a cyclic number.

It is not a de Polignac number, because 20309881 - 2⁷ = 20309753 is a prime.

It is a super-2 number, since 2×20309881² = 824982532468322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20309281) 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, 34366 + ... + 34951.

It is an arithmetic number, because the mean of its divisors is an integer number (5094873).

Almost surely, 2^20309881 is an apocalyptic number.

It is an amenable number.

20309881 is a deficient number, since it is larger than the sum of its proper divisors (69611).

20309881 is an equidigital number, since it uses as much as digits as its factorization.

20309881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69610.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 20309881 is about 4506.6485330010. The cubic root of 20309881 is about 272.8364936645.

It can be divided in two parts, 2030 and 9881, that added together give a palindrome (11911).

The spelling of 20309881 in words is "twenty million, three hundred nine thousand, eight hundred eighty-one".