991378673 has 2 divisors, whose sum is σ = 991378674. Its totient is φ = 991378672.

The previous prime is 991378669. The next prime is 991378691. The reversal of 991378673 is 376873199.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 978938944 + 12439729 = 31288^2 + 3527^2 .

It is a cyclic number.

It is not a de Polignac number, because 991378673 - 2² = 991378669 is a prime.

It is not a weakly prime, because it can be changed into another prime (991378603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495689336 + 495689337.

It is an arithmetic number, because the mean of its divisors is an integer number (495689337).

Almost surely, 2^991378673 is an apocalyptic number.

It is an amenable number.

991378673 is a deficient number, since it is larger than the sum of its proper divisors (1).

991378673 is an equidigital number, since it uses as much as digits as its factorization.

991378673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1714608, while the sum is 53.

The square root of 991378673 is about 31486.1663750924. The cubic root of 991378673 is about 997.1179259624.

The spelling of 991378673 in words is "nine hundred ninety-one million, three hundred seventy-eight thousand, six hundred seventy-three".