661415191 has 2 divisors, whose sum is σ = 661415192. Its totient is φ = 661415190.

The previous prime is 661415189. The next prime is 661415233. The reversal of 661415191 is 191514166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661415191 - 2¹ = 661415189 is a prime.

Together with 661415189, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661415171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330707595 + 330707596.

It is an arithmetic number, because the mean of its divisors is an integer number (330707596).

Almost surely, 2^661415191 is an apocalyptic number.

661415191 is a deficient number, since it is larger than the sum of its proper divisors (1).

661415191 is an equidigital number, since it uses as much as digits as its factorization.

661415191 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 34.

The square root of 661415191 is about 25717.9935259343. The cubic root of 661415191 is about 871.2806220630.

The spelling of 661415191 in words is "six hundred sixty-one million, four hundred fifteen thousand, one hundred ninety-one".