661415639 has 2 divisors, whose sum is σ = 661415640. Its totient is φ = 661415638.

The previous prime is 661415621. The next prime is 661415647. The reversal of 661415639 is 936514166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661415639 - 2¹⁶ = 661350103 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 661415596 and 661415605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661415539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330707819 + 330707820.

It is an arithmetic number, because the mean of its divisors is an integer number (330707820).

Almost surely, 2^661415639 is an apocalyptic number.

661415639 is a deficient number, since it is larger than the sum of its proper divisors (1).

661415639 is an equidigital number, since it uses as much as digits as its factorization.

661415639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 116640, while the sum is 41.

The square root of 661415639 is about 25718.0022357881. The cubic root of 661415639 is about 871.2808187794.

The spelling of 661415639 in words is "six hundred sixty-one million, four hundred fifteen thousand, six hundred thirty-nine".