641973981 has 8 divisors (see below), whose sum is σ = 933780384. Its totient is φ = 389075120.

The previous prime is 641973973. The next prime is 641973991. The reversal of 641973981 is 189379146.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 641973981 - 2³ = 641973973 is a prime.

It is a super-2 number, since 2×641973981² = 824261184561976722, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 641973981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641973901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9726846 + ... + 9726911.

It is an arithmetic number, because the mean of its divisors is an integer number (116722548).

Almost surely, 2^641973981 is an apocalyptic number.

It is an amenable number.

641973981 is a deficient number, since it is larger than the sum of its proper divisors (291806403).

641973981 is a wasteful number, since it uses less digits than its factorization.

641973981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19453771.

The product of its digits is 326592, while the sum is 48.

The square root of 641973981 is about 25337.2054694278. The cubic root of 641973981 is about 862.6589693959.

The spelling of 641973981 in words is "six hundred forty-one million, nine hundred seventy-three thousand, nine hundred eighty-one".