667956661 has 2 divisors, whose sum is σ = 667956662. Its totient is φ = 667956660.

The previous prime is 667956637. The next prime is 667956683. The reversal of 667956661 is 166659766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 496844100 + 171112561 = 22290^2 + 13081^2 .

It is a cyclic number.

It is not a de Polignac number, because 667956661 - 2¹³ = 667948469 is a prime.

It is a super-2 number, since 2×667956661² = 892332201948537842, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 667956599 and 667956608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (667926661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333978330 + 333978331.

It is an arithmetic number, because the mean of its divisors is an integer number (333978331).

Almost surely, 2^667956661 is an apocalyptic number.

It is an amenable number.

667956661 is a deficient number, since it is larger than the sum of its proper divisors (1).

667956661 is an equidigital number, since it uses as much as digits as its factorization.

667956661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2449440, while the sum is 52.

The square root of 667956661 is about 25844.8575349140. The cubic root of 667956661 is about 874.1435586230.

The spelling of 667956661 in words is "six hundred sixty-seven million, nine hundred fifty-six thousand, six hundred sixty-one".