6401664 has 48 divisors (see below), whose sum is σ = 18424770. Its totient is φ = 2133504.

The previous prime is 6401621. The next prime is 6401669. The reversal of 6401664 is 4661046.

6401664 is a `hidden beast` number, since 640 + 16 + 6 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 3968064 + 2433600 = 1992^2 + 1560^2 .

It is a tau number, because it is divible by the number of its divisors (48).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (6401669) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1627 + ... + 3930.

Almost surely, 2^6401664 is an apocalyptic number.

6401664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

6401664 is an abundant number, since it is smaller than the sum of its proper divisors (12023106).

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

6401664 is a wasteful number, since it uses less digits than its factorization.

6401664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5577 (or 5562 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 6401664 is about 2530.1509836371. The cubic root of 6401664 is about 185.6796427915.

It can be divided in two parts, 640 and 1664, that added together give a square (2304 = 48²).

The spelling of 6401664 in words is "six million, four hundred one thousand, six hundred sixty-four".