20856881 has 2 divisors, whose sum is σ = 20856882. Its totient is φ = 20856880.

The previous prime is 20856877. The next prime is 20856907. The reversal of 20856881 is 18865802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13653025 + 7203856 = 3695^2 + 2684^2 .

It is a cyclic number.

It is not a de Polignac number, because 20856881 - 2² = 20856877 is a prime.

It is a super-2 number, since 2×20856881² = 870018970096322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20856181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10428440 + 10428441.

It is an arithmetic number, because the mean of its divisors is an integer number (10428441).

Almost surely, 2^20856881 is an apocalyptic number.

It is an amenable number.

20856881 is a deficient number, since it is larger than the sum of its proper divisors (1).

20856881 is an equidigital number, since it uses as much as digits as its factorization.

20856881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30720, while the sum is 38.

The square root of 20856881 is about 4566.9334350306. The cubic root of 20856881 is about 275.2642352829.

The spelling of 20856881 in words is "twenty million, eight hundred fifty-six thousand, eight hundred eighty-one".