661563771 has 8 divisors (see below), whose sum is σ = 962274624. Its totient is φ = 400947720.

The previous prime is 661563739. The next prime is 661563787. The reversal of 661563771 is 177365166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661563771 - 2⁵ = 661563739 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661563731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10023661 + ... + 10023726.

It is an arithmetic number, because the mean of its divisors is an integer number (120284328).

Almost surely, 2^661563771 is an apocalyptic number.

661563771 is a deficient number, since it is larger than the sum of its proper divisors (300710853).

661563771 is a wasteful number, since it uses less digits than its factorization.

661563771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20047401.

The product of its digits is 158760, while the sum is 42.

The square root of 661563771 is about 25720.8820027619. The cubic root of 661563771 is about 871.3458585358.

The spelling of 661563771 in words is "six hundred sixty-one million, five hundred sixty-three thousand, seven hundred seventy-one".