721568617621 has 8 divisors (see below), whose sum is σ = 724433314784. Its totient is φ = 718709183280.

The previous prime is 721568617541. The next prime is 721568617643. The reversal of 721568617621 is 126716865127.

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 721568617621 - 2¹⁹ = 721568093333 is a prime.

It is a super-2 number, since 2×721568617621² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721568647621) 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, 1040835 + ... + 1589488.

It is an arithmetic number, because the mean of its divisors is an integer number (90554164348).

Almost surely, 2^721568617621 is an apocalyptic number.

It is an amenable number.

721568617621 is a deficient number, since it is larger than the sum of its proper divisors (2864697163).

721568617621 is a wasteful number, since it uses less digits than its factorization.

721568617621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2631411.

The product of its digits is 1693440, while the sum is 52.

The spelling of 721568617621 in words is "seven hundred twenty-one billion, five hundred sixty-eight million, six hundred seventeen thousand, six hundred twenty-one".