991604251 has 4 divisors (see below), whose sum is σ = 1081750104. Its totient is φ = 901458400.

The previous prime is 991604239. The next prime is 991604291. The reversal of 991604251 is 152406199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991604251 - 2²⁵ = 958049819 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 991604251.

It is not an unprimeable number, because it can be changed into a prime (991604291) 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 3 ways as a sum of consecutive naturals, for example, 45072910 + ... + 45072931.

It is an arithmetic number, because the mean of its divisors is an integer number (270437526).

Almost surely, 2^991604251 is an apocalyptic number.

991604251 is a deficient number, since it is larger than the sum of its proper divisors (90145853).

991604251 is a wasteful number, since it uses less digits than its factorization.

991604251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90145852.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 991604251 is about 31489.7483476766. The cubic root of 991604251 is about 997.1935481963.

The spelling of 991604251 in words is "nine hundred ninety-one million, six hundred four thousand, two hundred fifty-one".