866555381 has 2 divisors, whose sum is σ = 866555382. Its totient is φ = 866555380.

The previous prime is 866555359. The next prime is 866555449. The reversal of 866555381 is 183555668.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 525968356 + 340587025 = 22934^2 + 18455^2 .

It is a cyclic number.

It is not a de Polignac number, because 866555381 - 2⁶ = 866555317 is a prime.

It is a super-2 number, since 2×866555381² = 1501836456680110322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866555581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433277690 + 433277691.

It is an arithmetic number, because the mean of its divisors is an integer number (433277691).

Almost surely, 2^866555381 is an apocalyptic number.

It is an amenable number.

866555381 is a deficient number, since it is larger than the sum of its proper divisors (1).

866555381 is an equidigital number, since it uses as much as digits as its factorization.

866555381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864000, while the sum is 47.

The square root of 866555381 is about 29437.3127340116. The cubic root of 866555381 is about 953.3786918149.

It can be divided in two parts, 8665 and 55381, that added together give a palindrome (64046).

The spelling of 866555381 in words is "eight hundred sixty-six million, five hundred fifty-five thousand, three hundred eighty-one".