6639891840 has 128 divisors (see below), whose sum is σ = 23516344800. Its totient is φ = 1770633216.

The previous prime is 6639891833. The next prime is 6639891847. The reversal of 6639891840 is 481989366.

It is an interprime number because it is at equal distance from previous prime (6639891833) and next prime (6639891847).

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6639891847) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 174847 + ... + 209406.

Almost surely, 2^6639891840 is an apocalyptic number.

6639891840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

6639891840 is an abundant number, since it is smaller than the sum of its proper divisors (16876452960).

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

6639891840 is a wasteful number, since it uses less digits than its factorization.

6639891840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384281 (or 384263 counting only the distinct ones).

The product of its (nonzero) digits is 2239488, while the sum is 54.

The square root of 6639891840 is about 81485.5314764529. The cubic root of 6639891840 is about 1879.5490694567.

The spelling of 6639891840 in words is "six billion, six hundred thirty-nine million, eight hundred ninety-one thousand, eight hundred forty".