661415591 has 2 divisors, whose sum is σ = 661415592. Its totient is φ = 661415590.

The previous prime is 661415543. The next prime is 661415621. The reversal of 661415591 is 195514166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661415591 - 2⁶ = 661415527 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661415191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330707795 + 330707796.

It is an arithmetic number, because the mean of its divisors is an integer number (330707796).

Almost surely, 2^661415591 is an apocalyptic number.

661415591 is a deficient number, since it is larger than the sum of its proper divisors (1).

661415591 is an equidigital number, since it uses as much as digits as its factorization.

661415591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 38.

The square root of 661415591 is about 25718.0013025896. The cubic root of 661415591 is about 871.2807977026.

The spelling of 661415591 in words is "six hundred sixty-one million, four hundred fifteen thousand, five hundred ninety-one".