3945555661 has 2 divisors, whose sum is σ = 3945555662. Its totient is φ = 3945555660.

The previous prime is 3945555587. The next prime is 3945555689. The reversal of 3945555661 is 1665555493.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2368671561 + 1576884100 = 48669^2 + 39710^2 .

It is a cyclic number.

It is not a de Polignac number, because 3945555661 - 2⁷ = 3945555533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3945555461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1972777830 + 1972777831.

It is an arithmetic number, because the mean of its divisors is an integer number (1972777831).

Almost surely, 2^3945555661 is an apocalyptic number.

It is an amenable number.

3945555661 is a deficient number, since it is larger than the sum of its proper divisors (1).

3945555661 is an equidigital number, since it uses as much as digits as its factorization.

3945555661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2430000, while the sum is 49.

The square root of 3945555661 is about 62813.6582360875. The cubic root of 3945555661 is about 1580.1660431437.

The spelling of 3945555661 in words is "three billion, nine hundred forty-five million, five hundred fifty-five thousand, six hundred sixty-one".