721855843641 has 9 divisors (see below), whose sum is σ = 1042684344741. Its totient is φ = 481235529852.

The previous prime is 721855843627. The next prime is 721855843711. The reversal of 721855843641 is 146348558127.

It is a happy number.

The square root of 721855843641 is 849621.

It is a perfect power (a square), and thus also a powerful number.

721855843641 is a `hidden beast` number, since 7 + 2 + 1 + 8 + 558 + 43 + 6 + 41 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 721855843641 - 2¹⁷ = 721855712569 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721855843601) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2407260 + ... + 2690466.

Almost surely, 2^721855843641 is an apocalyptic number.

721855843641 is the 849621-st square number.

721855843641 is the 424811-st centered octagonal number.

It is an amenable number.

721855843641 is a deficient number, since it is larger than the sum of its proper divisors (320828501100).

721855843641 is an frugal number, since it uses more digits than its factorization.

721855843641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 566420 (or 283210 counting only the distinct ones).

The product of its digits is 6451200, while the sum is 54.

The spelling of 721855843641 in words is "seven hundred twenty-one billion, eight hundred fifty-five million, eight hundred forty-three thousand, six hundred forty-one".