991626917887 has 2 divisors, whose sum is σ = 991626917888. Its totient is φ = 991626917886.

The previous prime is 991626917851. The next prime is 991626917903. The reversal of 991626917887 is 788719626199.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991626917887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991626917287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495813458943 + 495813458944.

It is an arithmetic number, because the mean of its divisors is an integer number (495813458944).

Almost surely, 2^991626917887 is an apocalyptic number.

991626917887 is a deficient number, since it is larger than the sum of its proper divisors (1).

991626917887 is an equidigital number, since it uses as much as digits as its factorization.

991626917887 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 164602368, while the sum is 73.

The spelling of 991626917887 in words is "nine hundred ninety-one billion, six hundred twenty-six million, nine hundred seventeen thousand, eight hundred eighty-seven".