6642640399 has 4 divisors (see below), whose sum is σ = 6651879840. Its totient is φ = 6633400960.

The previous prime is 6642640393. The next prime is 6642640421. The reversal of 6642640399 is 9930462466.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6642640399 - 2⁷ = 6642640271 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6642640393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4618642 + ... + 4620079.

It is an arithmetic number, because the mean of its divisors is an integer number (1662969960).

Almost surely, 2^6642640399 is an apocalyptic number.

6642640399 is a deficient number, since it is larger than the sum of its proper divisors (9239441).

6642640399 is an equidigital number, since it uses as much as digits as its factorization.

6642640399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9239440.

The product of its (nonzero) digits is 1679616, while the sum is 49.

The square root of 6642640399 is about 81502.3950506977. The cubic root of 6642640399 is about 1879.8083778399.

The spelling of 6642640399 in words is "six billion, six hundred forty-two million, six hundred forty thousand, three hundred ninety-nine".