21991885 has 8 divisors (see below), whose sum is σ = 26580960. Its totient is φ = 17466384.

The previous prime is 21991883. The next prime is 21991891. The reversal of 21991885 is 58819912.

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

It is a cyclic number.

It is not a de Polignac number, because 21991885 - 2¹ = 21991883 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991883) 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, 15127 + ... + 16516.

It is an arithmetic number, because the mean of its divisors is an integer number (3322620).

Almost surely, 2^21991885 is an apocalyptic number.

It is an amenable number.

21991885 is a deficient number, since it is larger than the sum of its proper divisors (4589075).

21991885 is a wasteful number, since it uses less digits than its factorization.

21991885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31787.

The product of its digits is 51840, while the sum is 43.

The square root of 21991885 is about 4689.5506181296. The cubic root of 21991885 is about 280.1694764814.

The spelling of 21991885 in words is "twenty-one million, nine hundred ninety-one thousand, eight hundred eighty-five".