661711644 has 72 divisors (see below), whose sum is σ = 1838189808. Its totient is φ = 199038720.

The previous prime is 661711597. The next prime is 661711657. The reversal of 661711644 is 446117166.

It is a happy number.

661711644 is a `hidden beast` number, since 6 + 6 + 1 + 7 + 1 + 1 + 644 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 661711599 and 661711608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48154 + ... + 60350.

It is an arithmetic number, because the mean of its divisors is an integer number (25530414).

Almost surely, 2^661711644 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661711644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (919094904).

661711644 is an abundant number, since it is smaller than the sum of its proper divisors (1176478164).

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

661711644 is a wasteful number, since it uses less digits than its factorization.

661711644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12355 (or 12350 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 661711644 is about 25723.7564130902. The cubic root of 661711644 is about 871.4107748915.

The spelling of 661711644 in words is "six hundred sixty-one million, seven hundred eleven thousand, six hundred forty-four".