661691916 has 72 divisors (see below), whose sum is σ = 1747571280. Its totient is φ = 218909952.

The previous prime is 661691911. The next prime is 661691917. The reversal of 661691916 is 619196166.

661691916 is a `hidden beast` number, since 6 + 616 + 9 + 19 + 16 = 666.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (661691911) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 130680 + ... + 135648.

Almost surely, 2^661691916 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 661691916, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (873785640).

661691916 is an abundant number, since it is smaller than the sum of its proper divisors (1085879364).

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

661691916 is a wasteful number, since it uses less digits than its factorization.

661691916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5125 (or 5111 counting only the distinct ones).

The product of its digits is 104976, while the sum is 45.

The square root of 661691916 is about 25723.3729514619. The cubic root of 661691916 is about 871.4021148441.

The spelling of 661691916 in words is "six hundred sixty-one million, six hundred ninety-one thousand, nine hundred sixteen".