721717919 has 4 divisors (see below), whose sum is σ = 777234696. Its totient is φ = 666201144.

The previous prime is 721717873. The next prime is 721717921. The reversal of 721717919 is 919717127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 919717127 = 7 ⋅131388161.

It is a cyclic number.

It is not a de Polignac number, because 721717919 - 2⁸ = 721717663 is a prime.

It is a super-2 number, since 2×721717919² = 1041753509211381122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721717919.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721717979) 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, 27758369 + ... + 27758394.

It is an arithmetic number, because the mean of its divisors is an integer number (194308674).

Almost surely, 2^721717919 is an apocalyptic number.

721717919 is a deficient number, since it is larger than the sum of its proper divisors (55516777).

721717919 is a wasteful number, since it uses less digits than its factorization.

721717919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55516776.

The product of its digits is 55566, while the sum is 44.

The square root of 721717919 is about 26864.8081884089. The cubic root of 721717919 is about 896.9932248154.

The spelling of 721717919 in words is "seven hundred twenty-one million, seven hundred seventeen thousand, nine hundred nineteen".