6400640015 has 32 divisors (see below), whose sum is σ = 9585838080. Its totient is φ = 3985920000.

The previous prime is 6400639943. The next prime is 6400640017. The reversal of 6400640015 is 5100460046.

It is a happy number.

It is a Cunningham number, because it is equal to 80004²-1.

It is not a de Polignac number, because 6400640015 - 2²⁰ = 6399591439 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6400640017) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 392015 + ... + 408015.

It is an arithmetic number, because the mean of its divisors is an integer number (299557440).

Almost surely, 2^6400640015 is an apocalyptic number.

6400640015 is a deficient number, since it is larger than the sum of its proper divisors (3185198065).

6400640015 is a wasteful number, since it uses less digits than its factorization.

6400640015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17063.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 6400640015 is about 80003.9999937503. Note that the first 5 decimals coincide. The cubic root of 6400640015 is about 1856.6974206838.

The spelling of 6400640015 in words is "six billion, four hundred million, six hundred forty thousand, fifteen".