20640591 has 12 divisors (see below), whose sum is σ = 31110768. Its totient is φ = 13161984.

The previous prime is 20640583. The next prime is 20640617. The reversal of 20640591 is 19504602.

It is not a de Polignac number, because 20640591 - 2³ = 20640583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640511) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 49650 + ... + 50063.

It is an arithmetic number, because the mean of its divisors is an integer number (2592564).

Almost surely, 2^20640591 is an apocalyptic number.

20640591 is a deficient number, since it is larger than the sum of its proper divisors (10470177).

20640591 is a wasteful number, since it uses less digits than its factorization.

20640591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99742 (or 99739 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 20640591 is about 4543.1917194853. The cubic root of 20640591 is about 274.3094121312.

The spelling of 20640591 in words is "twenty million, six hundred forty thousand, five hundred ninety-one".