661797864 has 448 divisors, whose sum is σ = 2423836800. Its totient is φ = 164602368.

The previous prime is 661797853. The next prime is 661797901. The reversal of 661797864 is 468797166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (54).

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

It is a self number, because there is not a number n which added to its sum of digits gives 661797864.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 15390627 + ... + 15390669.

It is an arithmetic number, because the mean of its divisors is an integer number (5410350).

Almost surely, 2^661797864 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 661797864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1211918400).

661797864 is an abundant number, since it is smaller than the sum of its proper divisors (1762038936).

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

661797864 is a wasteful number, since it uses less digits than its factorization.

661797864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116 (or 97 counting only the distinct ones).

The product of its digits is 3048192, while the sum is 54.

The square root of 661797864 is about 25725.4322412666. The cubic root of 661797864 is about 871.4486210716.

The spelling of 661797864 in words is "six hundred sixty-one million, seven hundred ninety-seven thousand, eight hundred sixty-four".