21587745 has 16 divisors (see below), whose sum is σ = 35732160. Its totient is φ = 11116224.

The previous prime is 21587737. The next prime is 21587759. The reversal of 21587745 is 54778512.

It is not a de Polignac number, because 21587745 - 2³ = 21587737 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24379 + ... + 25248.

It is an arithmetic number, because the mean of its divisors is an integer number (2233260).

Almost surely, 2^21587745 is an apocalyptic number.

It is an amenable number.

21587745 is a deficient number, since it is larger than the sum of its proper divisors (14144415).

21587745 is a wasteful number, since it uses less digits than its factorization.

21587745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49664.

The product of its digits is 78400, while the sum is 39.

The square root of 21587745 is about 4646.2614003089. The cubic root of 21587745 is about 278.4426509129.

The spelling of 21587745 in words is "twenty-one million, five hundred eighty-seven thousand, seven hundred forty-five".