20809431 has 6 divisors (see below), whose sum is σ = 30058080. Its totient is φ = 13872948.

The previous prime is 20809423. The next prime is 20809433. The reversal of 20809431 is 13490802.

It is not a de Polignac number, because 20809431 - 2³ = 20809423 is a prime.

It is a super-2 number, since 2×20809431² = 866064837087522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20809395 and 20809404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809433) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1156071 + ... + 1156088.

It is an arithmetic number, because the mean of its divisors is an integer number (5009680).

Almost surely, 2^20809431 is an apocalyptic number.

20809431 is a deficient number, since it is larger than the sum of its proper divisors (9248649).

20809431 is a wasteful number, since it uses less digits than its factorization.

20809431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2312165 (or 2312162 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 20809431 is about 4561.7355249948. The cubic root of 20809431 is about 275.0553321167.

It can be divided in two parts, 2080 and 9431, that added together give a palindrome (11511).

The spelling of 20809431 in words is "twenty million, eight hundred nine thousand, four hundred thirty-one".