21887645 has 32 divisors (see below), whose sum is σ = 29804544. Its totient is φ = 15321600.

The previous prime is 21887641. The next prime is 21887647. The reversal of 21887645 is 54678812.

It is not a de Polignac number, because 21887645 - 2² = 21887641 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21887641) 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, 114500 + ... + 114690.

It is an arithmetic number, because the mean of its divisors is an integer number (931392).

Almost surely, 2^21887645 is an apocalyptic number.

It is an amenable number.

21887645 is a deficient number, since it is larger than the sum of its proper divisors (7916899).

21887645 is a wasteful number, since it uses less digits than its factorization.

21887645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293.

The product of its digits is 107520, while the sum is 41.

The square root of 21887645 is about 4678.4233455300. The cubic root of 21887645 is about 279.7261139845.

The spelling of 21887645 in words is "twenty-one million, eight hundred eighty-seven thousand, six hundred forty-five".