20891985 has 32 divisors (see below), whose sum is σ = 34836480. Its totient is φ = 10680000.

The previous prime is 20891971. The next prime is 20891989. The reversal of 20891985 is 58919802.

It is a happy number.

It is not a de Polignac number, because 20891985 - 2⁸ = 20891729 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20891989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 83110 + ... + 83360.

It is an arithmetic number, because the mean of its divisors is an integer number (1088640).

Almost surely, 2^20891985 is an apocalyptic number.

It is an amenable number.

20891985 is a deficient number, since it is larger than the sum of its proper divisors (13944495).

20891985 is a wasteful number, since it uses less digits than its factorization.

20891985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 20891985 is about 4570.7750983832. The cubic root of 20891985 is about 275.4185801826.

The spelling of 20891985 in words is "twenty million, eight hundred ninety-one thousand, nine hundred eighty-five".