5631021661 has 4 divisors (see below), whose sum is σ = 5631293052. Its totient is φ = 5630750272.

The previous prime is 5631021619. The next prime is 5631021689. The reversal of 5631021661 is 1661201365.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3170365636 + 2460656025 = 56306^2 + 49605^2 .

It is a cyclic number.

It is not a de Polignac number, because 5631021661 - 2⁷ = 5631021533 is a prime.

It is a Duffinian number.

It is a zygodrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5631021761) 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 in 3 ways as a sum of consecutive naturals, for example, 101740 + ... + 147013.

It is an arithmetic number, because the mean of its divisors is an integer number (1407823263).

Almost surely, 2^5631021661 is an apocalyptic number.

It is an amenable number.

5631021661 is a deficient number, since it is larger than the sum of its proper divisors (271391).

5631021661 is a wasteful number, since it uses less digits than its factorization.

5631021661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271390.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 5631021661 is about 75040.1336685910. The cubic root of 5631021661 is about 1779.0810453505.

The spelling of 5631021661 in words is "five billion, six hundred thirty-one million, twenty-one thousand, six hundred sixty-one".