721281606505 has 16 divisors (see below), whose sum is σ = 894783027600. Its totient is φ = 557786787840.

The previous prime is 721281606503. The next prime is 721281606541. The reversal of 721281606505 is 505606182127.

It can be written as a sum of positive squares in 8 ways, for example, as 1417597801 + 719864008704 = 37651^2 + 848448^2 .

It is not a de Polignac number, because 721281606505 - 2¹ = 721281606503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721281606503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16117320 + ... + 16162009.

It is an arithmetic number, because the mean of its divisors is an integer number (55923939225).

Almost surely, 2^721281606505 is an apocalyptic number.

It is an amenable number.

721281606505 is a deficient number, since it is larger than the sum of its proper divisors (173501421095).

721281606505 is a wasteful number, since it uses less digits than its factorization.

721281606505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32279484.

The product of its (nonzero) digits is 201600, while the sum is 43.

The spelling of 721281606505 in words is "seven hundred twenty-one billion, two hundred eighty-one million, six hundred six thousand, five hundred five".