861811257 has 4 divisors (see below), whose sum is σ = 1149081680. Its totient is φ = 574540836.

The previous prime is 861811229. The next prime is 861811303. The reversal of 861811257 is 752118168.

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 not a de Polignac number, because 861811257 - 2⁸ = 861811001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861811157) 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, 143635207 + ... + 143635212.

It is an arithmetic number, because the mean of its divisors is an integer number (287270420).

Almost surely, 2^861811257 is an apocalyptic number.

It is an amenable number.

861811257 is a deficient number, since it is larger than the sum of its proper divisors (287270423).

861811257 is a wasteful number, since it uses less digits than its factorization.

861811257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287270422.

The product of its digits is 26880, while the sum is 39.

The square root of 861811257 is about 29356.6220297908. The cubic root of 861811257 is about 951.6356888316.

The spelling of 861811257 in words is "eight hundred sixty-one million, eight hundred eleven thousand, two hundred fifty-seven".