5001561661 has 2 divisors, whose sum is σ = 5001561662. Its totient is φ = 5001561660.

The previous prime is 5001561563. The next prime is 5001561673. The reversal of 5001561661 is 1661651005.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3937562500 + 1063999161 = 62750^2 + 32619^2 .

It is a cyclic number.

It is not a de Polignac number, because 5001561661 - 2⁷ = 5001561533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (5001061661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2500780830 + 2500780831.

It is an arithmetic number, because the mean of its divisors is an integer number (2500780831).

Almost surely, 2^5001561661 is an apocalyptic number.

It is an amenable number.

5001561661 is a deficient number, since it is larger than the sum of its proper divisors (1).

5001561661 is an equidigital number, since it uses as much as digits as its factorization.

5001561661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5400, while the sum is 31.

The square root of 5001561661 is about 70721.7198673788. The cubic root of 5001561661 is about 1710.1539549952.

The spelling of 5001561661 in words is "five billion, one million, five hundred sixty-one thousand, six hundred sixty-one".