20906881 has 4 divisors (see below), whose sum is σ = 21218992. Its totient is φ = 20594772.

The previous prime is 20906863. The next prime is 20906903. The reversal of 20906881 is 18860902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20906881 - 2⁵ = 20906849 is a prime.

It is a super-2 number, since 2×20906881² = 874195346296322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20906801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 155955 + ... + 156088.

It is an arithmetic number, because the mean of its divisors is an integer number (5304748).

Almost surely, 2^20906881 is an apocalyptic number.

It is an amenable number.

20906881 is a deficient number, since it is larger than the sum of its proper divisors (312111).

20906881 is an equidigital number, since it uses as much as digits as its factorization.

20906881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312110.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 20906881 is about 4572.4042909612. The cubic root of 20906881 is about 275.4840225121.

The spelling of 20906881 in words is "twenty million, nine hundred six thousand, eight hundred eighty-one".