20511881 has 16 divisors (see below), whose sum is σ = 22982400. Its totient is φ = 18185088.

The previous prime is 20511871. The next prime is 20511889. The reversal of 20511881 is 18811502.

It is a cyclic number.

It is not a de Polignac number, because 20511881 - 2²² = 16317577 is a prime.

It is a super-2 number, since 2×20511881² = 841474524316322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20511881.

It is not an unprimeable number, because it can be changed into a prime (20511889) 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 15 ways as a sum of consecutive naturals, for example, 35765 + ... + 36333.

It is an arithmetic number, because the mean of its divisors is an integer number (1436400).

Almost surely, 2^20511881 is an apocalyptic number.

It is an amenable number.

20511881 is a deficient number, since it is larger than the sum of its proper divisors (2470519).

20511881 is a wasteful number, since it uses less digits than its factorization.

20511881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 688.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 20511881 is about 4529.0044159837. The cubic root of 20511881 is about 273.7380459463.

The spelling of 20511881 in words is "twenty million, five hundred eleven thousand, eight hundred eighty-one".