20640642 has 16 divisors (see below), whose sum is σ = 45034272. Its totient is φ = 6254720.

The previous prime is 20640617. The next prime is 20640647. The reversal of 20640642 is 24604602.

It is a super-2 number, since 2×20640642² = 852072204344328, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20640647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156303 + ... + 156434.

It is an arithmetic number, because the mean of its divisors is an integer number (2814642).

Almost surely, 2^20640642 is an apocalyptic number.

20640642 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

20640642 is an abundant number, since it is smaller than the sum of its proper divisors (24393630).

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

20640642 is a wasteful number, since it uses less digits than its factorization.

20640642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312753.

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 20640642 is about 4543.1973322760. The cubic root of 20640642 is about 274.3096380577.

The spelling of 20640642 in words is "twenty million, six hundred forty thousand, six hundred forty-two".