21608643 has 32 divisors (see below), whose sum is σ = 35799040. Its totient is φ = 11314080.

The previous prime is 21608641. The next prime is 21608663. The reversal of 21608643 is 34680612.

It is not a de Polignac number, because 21608643 - 2¹ = 21608641 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21608643.

It is not an unprimeable number, because it can be changed into a prime (21608641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 11496 + ... + 13242.

It is an arithmetic number, because the mean of its divisors is an integer number (1118720).

Almost surely, 2^21608643 is an apocalyptic number.

21608643 is a deficient number, since it is larger than the sum of its proper divisors (14190397).

21608643 is a wasteful number, since it uses less digits than its factorization.

21608643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1807.

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21608643 is about 4648.5097612030. The cubic root of 21608643 is about 278.5324706674.

The spelling of 21608643 in words is "twenty-one million, six hundred eight thousand, six hundred forty-three".