991673257 has 16 divisors (see below), whose sum is σ = 1074781440. Its totient is φ = 911409408.

The previous prime is 991673233. The next prime is 991673339. The reversal of 991673257 is 752376199.

It is a cyclic number.

It is not a de Polignac number, because 991673257 - 2¹⁹ = 991148969 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991673257.

It is not an unprimeable number, because it can be changed into a prime (991673227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 435919 + ... + 438187.

It is an arithmetic number, because the mean of its divisors is an integer number (67173840).

Almost surely, 2^991673257 is an apocalyptic number.

It is an amenable number.

991673257 is a deficient number, since it is larger than the sum of its proper divisors (83108183).

991673257 is a wasteful number, since it uses less digits than its factorization.

991673257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2880.

The product of its digits is 714420, while the sum is 49.

The square root of 991673257 is about 31490.8440185397. The cubic root of 991673257 is about 997.2166793133.

The spelling of 991673257 in words is "nine hundred ninety-one million, six hundred seventy-three thousand, two hundred fifty-seven".