861356781 has 16 divisors (see below), whose sum is σ = 1310574400. Its totient is φ = 558717264.

The previous prime is 861356767. The next prime is 861356803. The reversal of 861356781 is 187653168.

861356781 is a `hidden beast` number, since 8 + 6 + 1 + 3 + 567 + 81 = 666.

It is not a de Polignac number, because 861356781 - 2²⁷ = 727139053 is a prime.

It is a super-2 number, since 2×861356781² = 1483871008349363922, 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 (861356701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 430111 + ... + 432108.

It is an arithmetic number, because the mean of its divisors is an integer number (81910900).

Almost surely, 2^861356781 is an apocalyptic number.

It is an amenable number.

861356781 is a deficient number, since it is larger than the sum of its proper divisors (449217619).

861356781 is a wasteful number, since it uses less digits than its factorization.

861356781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 862265 (or 862259 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 861356781 is about 29348.8804045401. The cubic root of 861356781 is about 951.4683777854.

The spelling of 861356781 in words is "eight hundred sixty-one million, three hundred fifty-six thousand, seven hundred eighty-one".