641978784 has 72 divisors (see below), whose sum is σ = 1893265920. Its totient is φ = 213990336.

The previous prime is 641978773. The next prime is 641978789. The reversal of 641978784 is 487879146.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (72).

It is a super-2 number, since 2×641978784² = 824273518212237312, which contains 22 as substring.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

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

It is a self number, because there is not a number n which added to its sum of digits gives 641978784.

It is not an unprimeable number, because it can be changed into a prime (641978789) 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, 33504 + ... + 49055.

It is an arithmetic number, because the mean of its divisors is an integer number (26295360).

Almost surely, 2^641978784 is an apocalyptic number.

It is an amenable number.

641978784 is an abundant number, since it is smaller than the sum of its proper divisors (1251287136).

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

641978784 is an equidigital number, since it uses as much as digits as its factorization.

641978784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82584 (or 82564 counting only the distinct ones).

The product of its digits is 2709504, while the sum is 54.

The square root of 641978784 is about 25337.3002508160. The cubic root of 641978784 is about 862.6611207504.

The spelling of 641978784 in words is "six hundred forty-one million, nine hundred seventy-eight thousand, seven hundred eighty-four".