721961 has 2 divisors, whose sum is σ = 721962. Its totient is φ = 721960.

The previous prime is 721951. The next prime is 721979. The reversal of 721961 is 169127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 384400 + 337561 = 620^2 + 581^2 .

It is a cyclic number.

It is not a de Polignac number, because 721961 - 2¹⁸ = 459817 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 721961.

It is not a weakly prime, because it can be changed into another prime (721921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360980 + 360981.

It is an arithmetic number, because the mean of its divisors is an integer number (360981).

2⁷²¹⁹⁶¹ is an apocalyptic number.

It is an amenable number.

721961 is a deficient number, since it is larger than the sum of its proper divisors (1).

721961 is an equidigital number, since it uses as much as digits as its factorization.

721961 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 721961 is about 849.6828820213. The cubic root of 721961 is about 89.7093918604.

The spelling of 721961 in words is "seven hundred twenty-one thousand, nine hundred sixty-one".