20312640 has 112 divisors (see below), whose sum is σ = 71688960. Its totient is φ = 5414400.

The previous prime is 20312639. The next prime is 20312681. The reversal of 20312640 is 4621302.

It is a happy number.

20312640 is a `hidden beast` number, since 20 + 3 + 1 + 2 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7465 + ... + 9815.

It is an arithmetic number, because the mean of its divisors is an integer number (640080).

Almost surely, 2^20312640 is an apocalyptic number.

20312640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20312640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35844480).

20312640 is an abundant number, since it is smaller than the sum of its proper divisors (51376320).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20312640 is a wasteful number, since it uses less digits than its factorization.

20312640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2377 (or 2361 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 20312640 is about 4506.9546259087. The cubic root of 20312640 is about 272.8488476151.

Adding to 20312640 its reverse (4621302), we get a palindrome (24933942).

The spelling of 20312640 in words is "twenty million, three hundred twelve thousand, six hundred forty".