691919897 has 2 divisors, whose sum is σ = 691919898. Its totient is φ = 691919896.

The previous prime is 691919863. The next prime is 691919939. The reversal of 691919897 is 798919196.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 626050441 + 65869456 = 25021^2 + 8116^2 .

It is a cyclic number.

It is not a de Polignac number, because 691919897 - 2¹⁰ = 691918873 is a prime.

It is not a weakly prime, because it can be changed into another prime (691919857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345959948 + 345959949.

It is an arithmetic number, because the mean of its divisors is an integer number (345959949).

Almost surely, 2^691919897 is an apocalyptic number.

It is an amenable number.

691919897 is a deficient number, since it is larger than the sum of its proper divisors (1).

691919897 is an equidigital number, since it uses as much as digits as its factorization.

691919897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2204496, while the sum is 59.

The square root of 691919897 is about 26304.3703022901. The cubic root of 691919897 is about 884.4744118741.

The spelling of 691919897 in words is "six hundred ninety-one million, nine hundred nineteen thousand, eight hundred ninety-seven".