20871985 has 16 divisors (see below), whose sum is σ = 25812864. Its totient is φ = 16192512.

The previous prime is 20871973. The next prime is 20872003. The reversal of 20871985 is 58917802.

It is a cyclic number.

It is not a de Polignac number, because 20871985 - 2⁷ = 20871857 is a prime.

It is a super-4 number, since 4×20871985⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41244 + ... + 41746.

It is an arithmetic number, because the mean of its divisors is an integer number (1613304).

Almost surely, 2^20871985 is an apocalyptic number.

It is an amenable number.

20871985 is a deficient number, since it is larger than the sum of its proper divisors (4940879).

20871985 is a wasteful number, since it uses less digits than its factorization.

20871985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 744.

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

The square root of 20871985 is about 4568.5867617897. The cubic root of 20871985 is about 275.3306656025.

The spelling of 20871985 in words is "twenty million, eight hundred seventy-one thousand, nine hundred eighty-five".