20655781 has 4 divisors (see below), whose sum is σ = 21136192. Its totient is φ = 20175372.

The previous prime is 20655773. The next prime is 20655829. The reversal of 20655781 is 18755602.

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 20655781 - 2³ = 20655773 is a prime.

It is a super-2 number, since 2×20655781² = 853322577439922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20655751) 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, 240141 + ... + 240226.

It is an arithmetic number, because the mean of its divisors is an integer number (5284048).

Almost surely, 2^20655781 is an apocalyptic number.

It is an amenable number.

20655781 is a deficient number, since it is larger than the sum of its proper divisors (480411).

20655781 is an equidigital number, since it uses as much as digits as its factorization.

20655781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480410.

The product of its (nonzero) digits is 16800, while the sum is 34.

The square root of 20655781 is about 4544.8631442542. The cubic root of 20655781 is about 274.3766863393.

The spelling of 20655781 in words is "twenty million, six hundred fifty-five thousand, seven hundred eighty-one".