615721 has 2 divisors, whose sum is σ = 615722. Its totient is φ = 615720.

The previous prime is 615709. The next prime is 615731. The reversal of 615721 is 127516.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 547600 + 68121 = 740^2 + 261^2 .

It is a cyclic number.

It is not a de Polignac number, because 615721 - 2¹¹ = 613673 is a prime.

It is a super-2 number, since 2×615721² = 758224699682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 615692 and 615701.

It is not a weakly prime, because it can be changed into another prime (615731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 307860 + 307861.

It is an arithmetic number, because the mean of its divisors is an integer number (307861).

2⁶¹⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

615721 is a deficient number, since it is larger than the sum of its proper divisors (1).

615721 is an equidigital number, since it uses as much as digits as its factorization.

615721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 420, while the sum is 22.

The square root of 615721 is about 784.6789152258. The cubic root of 615721 is about 85.0735695234.

The spelling of 615721 in words is "six hundred fifteen thousand, seven hundred twenty-one".