661109831 has 2 divisors, whose sum is σ = 661109832. Its totient is φ = 661109830.

The previous prime is 661109819. The next prime is 661109851. The reversal of 661109831 is 138901166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661109831 - 2⁶ = 661109767 is a prime.

It is a super-2 number, since 2×661109831² = 874132417289697122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 661109791 and 661109800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661109851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330554915 + 330554916.

It is an arithmetic number, because the mean of its divisors is an integer number (330554916).

Almost surely, 2^661109831 is an apocalyptic number.

661109831 is a deficient number, since it is larger than the sum of its proper divisors (1).

661109831 is an equidigital number, since it uses as much as digits as its factorization.

661109831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 661109831 is about 25712.0561410401. The cubic root of 661109831 is about 871.1465180949.

The spelling of 661109831 in words is "six hundred sixty-one million, one hundred nine thousand, eight hundred thirty-one".