3505720721 has 2 divisors, whose sum is σ = 3505720722. Its totient is φ = 3505720720.

The previous prime is 3505720657. The next prime is 3505720759. The reversal of 3505720721 is 1270275053.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1926771025 + 1578949696 = 43895^2 + 39736^2 .

It is an emirp because it is prime and its reverse (1270275053) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3505720721 - 2⁶ = 3505720657 is a prime.

It is not a weakly prime, because it can be changed into another prime (3505720781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1752860360 + 1752860361.

It is an arithmetic number, because the mean of its divisors is an integer number (1752860361).

Almost surely, 2^3505720721 is an apocalyptic number.

It is an amenable number.

3505720721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3505720721 is an equidigital number, since it uses as much as digits as its factorization.

3505720721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14700, while the sum is 32.

The square root of 3505720721 is about 59209.1270075822. The cubic root of 3505720721 is about 1519.1212489079.

Adding to 3505720721 its reverse (1270275053), we get a palindrome (4775995774).

The spelling of 3505720721 in words is "three billion, five hundred five million, seven hundred twenty thousand, seven hundred twenty-one".