6439861620 has 36 divisors (see below), whose sum is σ = 19534247460. Its totient is φ = 1717296384.

The previous prime is 6439861583. The next prime is 6439861621. The reversal of 6439861620 is 261689346.

6439861620 is a `hidden beast` number, since 6 + 4 + 3 + 9 + 8 + 616 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 4851679716 + 1588181904 = 69654^2 + 39852^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6439861621) 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, 17888325 + ... + 17888684.

It is an arithmetic number, because the mean of its divisors is an integer number (542617985).

Almost surely, 2^6439861620 is an apocalyptic number.

6439861620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

6439861620 is an abundant number, since it is smaller than the sum of its proper divisors (13094385840).

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

6439861620 is a wasteful number, since it uses less digits than its factorization.

6439861620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35777024 (or 35777019 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 6439861620 is about 80248.7484014548. The cubic root of 6439861620 is about 1860.4821677475.

The spelling of 6439861620 in words is "six billion, four hundred thirty-nine million, eight hundred sixty-one thousand, six hundred twenty".