721503781 has 2 divisors, whose sum is σ = 721503782. Its totient is φ = 721503780.

The previous prime is 721503763. The next prime is 721503793. The reversal of 721503781 is 187305127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 716418756 + 5085025 = 26766^2 + 2255^2 .

It is a cyclic number.

It is not a de Polignac number, because 721503781 - 2¹⁵ = 721471013 is a prime.

It is a super-2 number, since 2×721503781² = 1041135411994591922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721503581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360751890 + 360751891.

It is an arithmetic number, because the mean of its divisors is an integer number (360751891).

Almost surely, 2^721503781 is an apocalyptic number.

It is an amenable number.

721503781 is a deficient number, since it is larger than the sum of its proper divisors (1).

721503781 is an equidigital number, since it uses as much as digits as its factorization.

721503781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11760, while the sum is 34.

The square root of 721503781 is about 26860.8224185337. The cubic root of 721503781 is about 896.9045016313.

The spelling of 721503781 in words is "seven hundred twenty-one million, five hundred three thousand, seven hundred eighty-one".