20640825 has 30 divisors (see below), whose sum is σ = 38237694. Its totient is φ = 11007360.

The previous prime is 20640793. The next prime is 20640827. The reversal of 20640825 is 52804602.

It can be written as a sum of positive squares in 3 ways, for example, as 2595321 + 18045504 = 1611^2 + 4248^2 .

It is not a de Polignac number, because 20640825 - 2⁵ = 20640793 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (20640827) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 3072 + ... + 7121.

Almost surely, 2^20640825 is an apocalyptic number.

20640825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

20640825 is a deficient number, since it is larger than the sum of its proper divisors (17596869).

20640825 is a wasteful number, since it uses less digits than its factorization.

20640825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10215 (or 10201 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 20640825 is about 4543.2174722326. The cubic root of 20640825 is about 274.3104487320.

The spelling of 20640825 in words is "twenty million, six hundred forty thousand, eight hundred twenty-five".