661424400 has 480 divisors, whose sum is σ = 2901758720. Its totient is φ = 139345920.

The previous prime is 661424399. The next prime is 661424429. The reversal of 661424400 is 4424166.

661424400 is a `hidden beast` number, since 6 + 614 + 2 + 4 + 40 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 982464 + ... + 983136.

Almost surely, 2^661424400 is an apocalyptic number.

661424400 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661424400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1450879360).

661424400 is an abundant number, since it is smaller than the sum of its proper divisors (2240334320).

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

661424400 is a wasteful number, since it uses less digits than its factorization.

661424400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 720 (or 703 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 27.

The square root of 661424400 is about 25718.1725633840. The cubic root of 661424400 is about 871.2846657086.

Adding to 661424400 its reverse (4424166), we get a palindrome (665848566).

The spelling of 661424400 in words is "six hundred sixty-one million, four hundred twenty-four thousand, four hundred".