721213981861 has 2 divisors, whose sum is σ = 721213981862. Its totient is φ = 721213981860.

The previous prime is 721213981801. The next prime is 721213981919. The reversal of 721213981861 is 168189312127.

721213981861 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 475505405761 + 245708576100 = 689569^2 + 495690^2 .

It is an emirp because it is prime and its reverse (168189312127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721213981861 - 2⁹ = 721213981349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721213981801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360606990930 + 360606990931.

It is an arithmetic number, because the mean of its divisors is an integer number (360606990931).

Almost surely, 2^721213981861 is an apocalyptic number.

It is an amenable number.

721213981861 is a deficient number, since it is larger than the sum of its proper divisors (1).

721213981861 is an equidigital number, since it uses as much as digits as its factorization.

721213981861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 49.

The spelling of 721213981861 in words is "seven hundred twenty-one billion, two hundred thirteen million, nine hundred eighty-one thousand, eight hundred sixty-one".