721369661 has 2 divisors, whose sum is σ = 721369662. Its totient is φ = 721369660.

The previous prime is 721369657. The next prime is 721369669. The reversal of 721369661 is 166963127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 590976100 + 130393561 = 24310^2 + 11419^2 .

It is a cyclic number.

It is not a de Polignac number, because 721369661 - 2² = 721369657 is a prime.

It is a super-2 number, since 2×721369661² = 1040748375622509842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721369669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360684830 + 360684831.

It is an arithmetic number, because the mean of its divisors is an integer number (360684831).

Almost surely, 2^721369661 is an apocalyptic number.

It is an amenable number.

721369661 is a deficient number, since it is larger than the sum of its proper divisors (1).

721369661 is an equidigital number, since it uses as much as digits as its factorization.

721369661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81648, while the sum is 41.

The square root of 721369661 is about 26858.3257296504. The cubic root of 721369661 is about 896.8489231347.

The spelling of 721369661 in words is "seven hundred twenty-one million, three hundred sixty-nine thousand, six hundred sixty-one".