661977400 has 96 divisors (see below), whose sum is σ = 1767565440. Its totient is φ = 225855360.

The previous prime is 661977377. The next prime is 661977401. The reversal of 661977400 is 4779166.

It is a super-2 number, since 2×661977400² = 876428156221520000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661977401) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 316759 + ... + 318841.

It is an arithmetic number, because the mean of its divisors is an integer number (18412140).

Almost surely, 2^661977400 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 661977400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (883782720).

661977400 is an abundant number, since it is smaller than the sum of its proper divisors (1105588040).

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

661977400 is a wasteful number, since it uses less digits than its factorization.

661977400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2333 (or 2324 counting only the distinct ones).

The product of its (nonzero) digits is 63504, while the sum is 40.

The square root of 661977400 is about 25728.9214698168. The cubic root of 661977400 is about 871.5274176660.

The spelling of 661977400 in words is "six hundred sixty-one million, nine hundred seventy-seven thousand, four hundred".