991378607 has 2 divisors, whose sum is σ = 991378608. Its totient is φ = 991378606.

The previous prime is 991378603. The next prime is 991378627. The reversal of 991378607 is 706873199.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991378607 - 2² = 991378603 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991378603) 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 as a sum of consecutive naturals, namely, 495689303 + 495689304.

It is an arithmetic number, because the mean of its divisors is an integer number (495689304).

Almost surely, 2^991378607 is an apocalyptic number.

991378607 is a deficient number, since it is larger than the sum of its proper divisors (1).

991378607 is an equidigital number, since it uses as much as digits as its factorization.

991378607 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 571536, while the sum is 50.

The square root of 991378607 is about 31486.1653270131. The cubic root of 991378607 is about 997.1179038351.

The spelling of 991378607 in words is "nine hundred ninety-one million, three hundred seventy-eight thousand, six hundred seven".