21807985 has 8 divisors (see below), whose sum is σ = 26877096. Its totient is φ = 16974720.

The previous prime is 21807959. The next prime is 21808013. The reversal of 21807985 is 58970812.

It can be written as a sum of positive squares in 4 ways, for example, as 11771761 + 10036224 = 3431^2 + 3168^2 .

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

It is not a de Polignac number, because 21807985 - 2²¹ = 19710833 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58756 + ... + 59125.

It is an arithmetic number, because the mean of its divisors is an integer number (3359637).

Almost surely, 2^21807985 is an apocalyptic number.

It is an amenable number.

21807985 is a deficient number, since it is larger than the sum of its proper divisors (5069111).

21807985 is a wasteful number, since it uses less digits than its factorization.

21807985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117923.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 21807985 is about 4669.9020332337. The cubic root of 21807985 is about 279.3863474180.

The spelling of 21807985 in words is "twenty-one million, eight hundred seven thousand, nine hundred eighty-five".