721619 has 2 divisors, whose sum is σ = 721620. Its totient is φ = 721618.

The previous prime is 721613. The next prime is 721621. The reversal of 721619 is 916127.

It is a strong prime.

It is an emirp because it is prime and its reverse (916127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721619 - 2⁸ = 721363 is a prime.

It is a super-2 number, since 2×721619² = 1041467962322, which contains 22 as substring.

Together with 721621, it forms a pair of twin primes.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721619.

It is not a weakly prime, because it can be changed into another prime (721613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360809 + 360810.

It is an arithmetic number, because the mean of its divisors is an integer number (360810).

2⁷²¹⁶¹⁹ is an apocalyptic number.

721619 is a deficient number, since it is larger than the sum of its proper divisors (1).

721619 is an equidigital number, since it uses as much as digits as its factorization.

721619 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 756, while the sum is 26.

The square root of 721619 is about 849.4816066284. The cubic root of 721619 is about 89.6952242171.

The spelling of 721619 in words is "seven hundred twenty-one thousand, six hundred nineteen".