651549991 has 2 divisors, whose sum is σ = 651549992. Its totient is φ = 651549990.

The previous prime is 651549961. The next prime is 651550037. The reversal of 651549991 is 199945156.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 651549991 - 2⁵ = 651549959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (651549961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 325774995 + 325774996.

It is an arithmetic number, because the mean of its divisors is an integer number (325774996).

Almost surely, 2^651549991 is an apocalyptic number.

651549991 is a deficient number, since it is larger than the sum of its proper divisors (1).

651549991 is an equidigital number, since it uses as much as digits as its factorization.

651549991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 437400, while the sum is 49.

The square root of 651549991 is about 25525.4772923054. The cubic root of 651549991 is about 866.9271037974.

The spelling of 651549991 in words is "six hundred fifty-one million, five hundred forty-nine thousand, nine hundred ninety-one".