721206217 has 2 divisors, whose sum is σ = 721206218. Its totient is φ = 721206216.

The previous prime is 721206137. The next prime is 721206251. The reversal of 721206217 is 712602127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 479434816 + 241771401 = 21896^2 + 15549^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721206217 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721207217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360603108 + 360603109.

It is an arithmetic number, because the mean of its divisors is an integer number (360603109).

Almost surely, 2^721206217 is an apocalyptic number.

It is an amenable number.

721206217 is a deficient number, since it is larger than the sum of its proper divisors (1).

721206217 is an equidigital number, since it uses as much as digits as its factorization.

721206217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2352, while the sum is 28.

The square root of 721206217 is about 26855.2828508657. The cubic root of 721206217 is about 896.7811836407.

The spelling of 721206217 in words is "seven hundred twenty-one million, two hundred six thousand, two hundred seventeen".