20909639 has 4 divisors (see below), whose sum is σ = 20987640. Its totient is φ = 20831640.

The previous prime is 20909621. The next prime is 20909657. The reversal of 20909639 is 93690902.

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 (20909621) and next prime (20909657).

It is a cyclic number.

It is not a de Polignac number, because 20909639 - 2²⁰ = 19861063 is a prime.

It is a super-2 number, since 2×20909639² = 874426006220642, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20909039) 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, 38597 + ... + 39134.

It is an arithmetic number, because the mean of its divisors is an integer number (5246910).

Almost surely, 2^20909639 is an apocalyptic number.

20909639 is a deficient number, since it is larger than the sum of its proper divisors (78001).

20909639 is an equidigital number, since it uses as much as digits as its factorization.

20909639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78000.

The product of its (nonzero) digits is 26244, while the sum is 38.

The square root of 20909639 is about 4572.7058728941. The cubic root of 20909639 is about 275.4961357732.

The spelling of 20909639 in words is "twenty million, nine hundred nine thousand, six hundred thirty-nine".