661640742 has 96 divisors (see below), whose sum is σ = 1734670080. Its totient is φ = 178234560.

The previous prime is 661640689. The next prime is 661640773. The reversal of 661640742 is 247046166.

661640742 is a `hidden beast` number, since 6 + 6 + 1 + 640 + 7 + 4 + 2 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 661640697 and 661640706.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 155017 + ... + 159227.

It is an arithmetic number, because the mean of its divisors is an integer number (18069480).

Almost surely, 2^661640742 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661640742, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (867335040).

661640742 is an abundant number, since it is smaller than the sum of its proper divisors (1073029338).

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

661640742 is a wasteful number, since it uses less digits than its factorization.

661640742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4298 (or 4295 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 661640742 is about 25722.3782337481. The cubic root of 661640742 is about 871.3796500684.

The spelling of 661640742 in words is "six hundred sixty-one million, six hundred forty thousand, seven hundred forty-two".