20915643 has 8 divisors (see below), whose sum is σ = 31871488. Its totient is φ = 11951784.

The previous prime is 20915597. The next prime is 20915651. The reversal of 20915643 is 34651902.

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

It is not a de Polignac number, because 20915643 - 2⁸ = 20915387 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20915643.

It is not an unprimeable number, because it can be changed into a prime (20915663) 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, 497971 + ... + 498012.

It is an arithmetic number, because the mean of its divisors is an integer number (3983936).

Almost surely, 2^20915643 is an apocalyptic number.

20915643 is a deficient number, since it is larger than the sum of its proper divisors (10955845).

20915643 is an equidigital number, since it uses as much as digits as its factorization.

20915643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 995993.

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 20915643 is about 4573.3623298400. The cubic root of 20915643 is about 275.5225019307.

The spelling of 20915643 in words is "twenty million, nine hundred fifteen thousand, six hundred forty-three".