21929985 has 48 divisors (see below), whose sum is σ = 47399040. Its totient is φ = 9112320.

The previous prime is 21929977. The next prime is 21929987. The reversal of 21929985 is 58992912.

It is not a de Polignac number, because 21929985 - 2³ = 21929977 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21929985.

It is not an unprimeable number, because it can be changed into a prime (21929987) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 301 + ... + 6629.

It is an arithmetic number, because the mean of its divisors is an integer number (987480).

It is a Proth number, since it is equal to 2677 ⋅ 2¹³ + 1 and 2677 < 2¹³.

Almost surely, 2^21929985 is an apocalyptic number.

It is an amenable number.

21929985 is an abundant number, since it is smaller than the sum of its proper divisors (25469055).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21929985 is a wasteful number, since it uses less digits than its factorization.

21929985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6358 (or 6355 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 21929985 is about 4682.9461880316. The cubic root of 21929985 is about 279.9063675021.

The spelling of 21929985 in words is "twenty-one million, nine hundred twenty-nine thousand, nine hundred eighty-five".