20856805381 has 4 divisors (see below), whose sum is σ = 21954532000. Its totient is φ = 19759078764.

The previous prime is 20856805379. The next prime is 20856805427. The reversal of 20856805381 is 18350865802.

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 20856805381 - 2¹ = 20856805379 is a prime.

It is a super-2 number, since 2×20856805381² (a number of 21 digits) 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 (20856800381) 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, 548863281 + ... + 548863318.

It is an arithmetic number, because the mean of its divisors is an integer number (5488633000).

Almost surely, 2^20856805381 is an apocalyptic number.

It is an amenable number.

20856805381 is a deficient number, since it is larger than the sum of its proper divisors (1097726619).

20856805381 is a wasteful number, since it uses less digits than its factorization.

20856805381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1097726618.

The product of its (nonzero) digits is 460800, while the sum is 46.

The spelling of 20856805381 in words is "twenty billion, eight hundred fifty-six million, eight hundred five thousand, three hundred eighty-one".