21985491 has 16 divisors (see below), whose sum is σ = 32215680. Its totient is φ = 13225920.

The previous prime is 21985477. The next prime is 21985499. The reversal of 21985491 is 19458912.

It is not a de Polignac number, because 21985491 - 2⁵ = 21985459 is a prime.

It is a super-2 number, since 2×21985491² = 966723629022162, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21985499) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2191 + ... + 6983.

It is an arithmetic number, because the mean of its divisors is an integer number (2013480).

Almost surely, 2^21985491 is an apocalyptic number.

21985491 is a deficient number, since it is larger than the sum of its proper divisors (10230189).

21985491 is a wasteful number, since it uses less digits than its factorization.

21985491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4946.

The product of its digits is 25920, while the sum is 39.

The square root of 21985491 is about 4688.8688401362. The cubic root of 21985491 is about 280.1423213546.

The spelling of 21985491 in words is "twenty-one million, nine hundred eighty-five thousand, four hundred ninety-one".