20640513 has 8 divisors (see below), whose sum is σ = 28408576. Its totient is φ = 13316400.

The previous prime is 20640511. The next prime is 20640541. The reversal of 20640513 is 31504602.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20640513 - 2¹ = 20640511 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20640513.

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 7 ways as a sum of consecutive naturals, for example, 110878 + ... + 111063.

It is an arithmetic number, because the mean of its divisors is an integer number (3551072).

Almost surely, 2^20640513 is an apocalyptic number.

It is an amenable number.

20640513 is a deficient number, since it is larger than the sum of its proper divisors (7768063).

20640513 is a wasteful number, since it uses less digits than its factorization.

20640513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221975.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 20640513 is about 4543.1831352038. The cubic root of 20640513 is about 274.3090665959.

The spelling of 20640513 in words is "twenty million, six hundred forty thousand, five hundred thirteen".