6440664437 has 4 divisors (see below), whose sum is σ = 6445269600. Its totient is φ = 6436059276.

The previous prime is 6440664431. The next prime is 6440664449. The reversal of 6440664437 is 7344660446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7344660446 = 2 ⋅3672330223.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6440664437 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6440664431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2300483 + ... + 2303280.

It is an arithmetic number, because the mean of its divisors is an integer number (1611317400).

Almost surely, 2^6440664437 is an apocalyptic number.

It is an amenable number.

6440664437 is a deficient number, since it is larger than the sum of its proper divisors (4605163).

6440664437 is a wasteful number, since it uses less digits than its factorization.

6440664437 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4605162.

The product of its (nonzero) digits is 1161216, while the sum is 44.

The square root of 6440664437 is about 80253.7502986621. The cubic root of 6440664437 is about 1860.5594760675.

The spelling of 6440664437 in words is "six billion, four hundred forty million, six hundred sixty-four thousand, four hundred thirty-seven".