20689881 has 4 divisors (see below), whose sum is σ = 27586512. Its totient is φ = 13793252.

The previous prime is 20689873. The next prime is 20689883. The reversal of 20689881 is 18898602.

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 20689881 - 2³ = 20689873 is a prime.

It is a super-2 number, since 2×20689881² = 856142351588322, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20689883) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3448311 + ... + 3448316.

It is an arithmetic number, because the mean of its divisors is an integer number (6896628).

Almost surely, 2^20689881 is an apocalyptic number.

It is an amenable number.

20689881 is a deficient number, since it is larger than the sum of its proper divisors (6896631).

20689881 is an equidigital number, since it uses as much as digits as its factorization.

20689881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6896630.

The product of its (nonzero) digits is 55296, while the sum is 42.

The square root of 20689881 is about 4548.6130853261. The cubic root of 20689881 is about 274.5275900351.

The spelling of 20689881 in words is "twenty million, six hundred eighty-nine thousand, eight hundred eighty-one".