721620749 has 2 divisors, whose sum is σ = 721620750. Its totient is φ = 721620748.

The previous prime is 721620689. The next prime is 721620763. The reversal of 721620749 is 947026127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 382398025 + 339222724 = 19555^2 + 18418^2 .

It is a cyclic number.

It is not a de Polignac number, because 721620749 - 2²⁰ = 720572173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721620349) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360810374 + 360810375.

It is an arithmetic number, because the mean of its divisors is an integer number (360810375).

Almost surely, 2^721620749 is an apocalyptic number.

It is an amenable number.

721620749 is a deficient number, since it is larger than the sum of its proper divisors (1).

721620749 is an equidigital number, since it uses as much as digits as its factorization.

721620749 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42336, while the sum is 38.

The square root of 721620749 is about 26862.9996277408. Note that the first 3 decimals coincide. The cubic root of 721620749 is about 896.9529668229.

The spelling of 721620749 in words is "seven hundred twenty-one million, six hundred twenty thousand, seven hundred forty-nine".