721440857 has 2 divisors, whose sum is σ = 721440858. Its totient is φ = 721440856.

The previous prime is 721440847. The next prime is 721440947. The reversal of 721440857 is 758044127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 668791321 + 52649536 = 25861^2 + 7256^2 .

It is a cyclic number.

It is not a de Polignac number, because 721440857 - 2¹² = 721436761 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 721440857.

It is not a weakly prime, because it can be changed into another prime (721440817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360720428 + 360720429.

It is an arithmetic number, because the mean of its divisors is an integer number (360720429).

Almost surely, 2^721440857 is an apocalyptic number.

It is an amenable number.

721440857 is a deficient number, since it is larger than the sum of its proper divisors (1).

721440857 is an equidigital number, since it uses as much as digits as its factorization.

721440857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62720, while the sum is 38.

The square root of 721440857 is about 26859.6510960213. The cubic root of 721440857 is about 896.8784271735.

The spelling of 721440857 in words is "seven hundred twenty-one million, four hundred forty thousand, eight hundred fifty-seven".