65815991 has 2 divisors, whose sum is σ = 65815992. Its totient is φ = 65815990.

The previous prime is 65815987. The next prime is 65815999. The reversal of 65815991 is 19951856.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 65815991 - 2² = 65815987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (65815999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32907995 + 32907996.

It is an arithmetic number, because the mean of its divisors is an integer number (32907996).

Almost surely, 2^65815991 is an apocalyptic number.

65815991 is a deficient number, since it is larger than the sum of its proper divisors (1).

65815991 is an equidigital number, since it uses as much as digits as its factorization.

65815991 is an evil number, because the sum of its binary digits is even.

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

The square root of 65815991 is about 8112.7055289835. The cubic root of 65815991 is about 403.7480845439.

The spelling of 65815991 in words is "sixty-five million, eight hundred fifteen thousand, nine hundred ninety-one".