640969647840 has 144 divisors (see below), whose sum is σ = 2238176788848. Its totient is φ = 166950217728.

The previous prime is 640969647839. The next prime is 640969647841. The reversal of 640969647840 is 48746969046.

640969647840 is a `hidden beast` number, since 6 + 409 + 69 + 64 + 78 + 40 = 666.

It is an interprime number because it is at equal distance from previous prime (640969647839) and next prime (640969647841).

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640969647841) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5113869 + ... + 5237708.

It is an arithmetic number, because the mean of its divisors is an integer number (15542894367).

Almost surely, 2^640969647840 is an apocalyptic number.

640969647840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640969647840 is an abundant number, since it is smaller than the sum of its proper divisors (1597207141008).

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

640969647840 is a wasteful number, since it uses less digits than its factorization.

640969647840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10351641 (or 10351630 counting only the distinct ones).

The product of its (nonzero) digits is 62705664, while the sum is 63.

The spelling of 640969647840 in words is "six hundred forty billion, nine hundred sixty-nine million, six hundred forty-seven thousand, eight hundred forty".