991975897 has 4 divisors (see below), whose sum is σ = 1082155536. Its totient is φ = 901796260.

The previous prime is 991975889. The next prime is 991975939. The reversal of 991975897 is 798579199.

991975897 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 991975897 - 2³ = 991975889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991975837) 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, 45089803 + ... + 45089824.

It is an arithmetic number, because the mean of its divisors is an integer number (270538884).

Almost surely, 2^991975897 is an apocalyptic number.

It is an amenable number.

991975897 is a deficient number, since it is larger than the sum of its proper divisors (90179639).

991975897 is a wasteful number, since it uses less digits than its factorization.

991975897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90179638.

The product of its digits is 12859560, while the sum is 64.

The square root of 991975897 is about 31495.6488582153. The cubic root of 991975897 is about 997.3181129115.

The spelling of 991975897 in words is "nine hundred ninety-one million, nine hundred seventy-five thousand, eight hundred ninety-seven".