991805651 has 2 divisors, whose sum is σ = 991805652. Its totient is φ = 991805650.

The previous prime is 991805629. The next prime is 991805669. The reversal of 991805651 is 156508199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991805651 - 2²² = 987611347 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (991805251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495902825 + 495902826.

It is an arithmetic number, because the mean of its divisors is an integer number (495902826).

Almost surely, 2^991805651 is an apocalyptic number.

991805651 is a deficient number, since it is larger than the sum of its proper divisors (1).

991805651 is an equidigital number, since it uses as much as digits as its factorization.

991805651 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 97200, while the sum is 44.

The square root of 991805651 is about 31492.9460514573. The cubic root of 991805651 is about 997.2610553646.

The spelling of 991805651 in words is "nine hundred ninety-one million, eight hundred five thousand, six hundred fifty-one".