721645423399 has 4 divisors (see below), whose sum is σ = 721647161136. Its totient is φ = 721643685664.

The previous prime is 721645423397. The next prime is 721645423409. The reversal of 721645423399 is 993324546127.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 993324546127 = 123757 ⋅8026411.

It is a cyclic number.

It is not a de Polignac number, because 721645423399 - 2¹ = 721645423397 is a prime.

It is a super-2 number, since 2×721645423399² (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 (721645423397) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 160767 + ... + 1212079.

It is an arithmetic number, because the mean of its divisors is an integer number (180411790284).

Almost surely, 2^721645423399 is an apocalyptic number.

721645423399 is a deficient number, since it is larger than the sum of its proper divisors (1737737).

721645423399 is a wasteful number, since it uses less digits than its factorization.

721645423399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1737736.

The product of its digits is 9797760, while the sum is 55.

The spelling of 721645423399 in words is "seven hundred twenty-one billion, six hundred forty-five million, four hundred twenty-three thousand, three hundred ninety-nine".