851431591921 has 4 divisors (see below), whose sum is σ = 852602750272. Its totient is φ = 850260433572.

The previous prime is 851431591909. The next prime is 851431591957. The reversal of 851431591921 is 129195134158.

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 851431591921 - 2⁷ = 851431591793 is a prime.

It is a super-2 number, since 2×851431591921² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (851431591961) 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, 585578085 + ... + 585579538.

It is an arithmetic number, because the mean of its divisors is an integer number (213150687568).

Almost surely, 2^851431591921 is an apocalyptic number.

It is an amenable number.

851431591921 is a deficient number, since it is larger than the sum of its proper divisors (1171158351).

851431591921 is a wasteful number, since it uses less digits than its factorization.

851431591921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1171158350.

The product of its digits is 388800, while the sum is 49.

The spelling of 851431591921 in words is "eight hundred fifty-one billion, four hundred thirty-one million, five hundred ninety-one thousand, nine hundred twenty-one".