664640400 has 60 divisors (see below), whose sum is σ = 2129068592. Its totient is φ = 177237120.

The previous prime is 664640377. The next prime is 664640401. The reversal of 664640400 is 4046466.

It is a tau number, because it is divible by the number of its divisors (60).

It is a super-2 number, since 2×664640400² = 883493722624320000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (664640401) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 275734 + ... + 278133.

Almost surely, 2^664640400 is an apocalyptic number.

664640400 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

664640400 is an abundant number, since it is smaller than the sum of its proper divisors (1464428192).

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

664640400 is a wasteful number, since it uses less digits than its factorization.

664640400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 553888 (or 553877 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 664640400 is about 25780.6206286815. The cubic root of 664640400 is about 872.6945130538.

Adding to 664640400 its reverse (4046466), we get a palindrome (668686866).

The spelling of 664640400 in words is "six hundred sixty-four million, six hundred forty thousand, four hundred".