661563126 has 256 divisors, whose sum is σ = 1904394240. Its totient is φ = 167961600.

The previous prime is 661563113. The next prime is 661563137. The reversal of 661563126 is 621365166.

661563126 is a `hidden beast` number, since 6 + 6 + 15 + 631 + 2 + 6 = 666.

It is a congruent number.

It is an unprimeable number.

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 127 ways as a sum of consecutive naturals, for example, 16135666 + ... + 16135706.

It is an arithmetic number, because the mean of its divisors is an integer number (7439040).

Almost surely, 2^661563126 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661563126, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (952197120).

661563126 is an abundant number, since it is smaller than the sum of its proper divisors (1242831114).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661563126 is a wasteful number, since it uses less digits than its factorization.

661563126 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119 (or 101 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 661563126 is about 25720.8694643086. The cubic root of 661563126 is about 871.3455753592.

The spelling of 661563126 in words is "six hundred sixty-one million, five hundred sixty-three thousand, one hundred twenty-six".