20765639 has 4 divisors (see below), whose sum is σ = 21272160. Its totient is φ = 20259120.

The previous prime is 20765617. The next prime is 20765669. The reversal of 20765639 is 93656702.

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

It is a cyclic number.

It is not a de Polignac number, because 20765639 - 2¹⁶ = 20700103 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20765609) 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, 253199 + ... + 253280.

It is an arithmetic number, because the mean of its divisors is an integer number (5318040).

Almost surely, 2^20765639 is an apocalyptic number.

20765639 is a deficient number, since it is larger than the sum of its proper divisors (506521).

20765639 is an equidigital number, since it uses as much as digits as its factorization.

20765639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 506520.

The product of its (nonzero) digits is 68040, while the sum is 38.

The square root of 20765639 is about 4556.9330695107. The cubic root of 20765639 is about 274.8622516741.

The spelling of 20765639 in words is "twenty million, seven hundred sixty-five thousand, six hundred thirty-nine".