7212781805 has 18 divisors (see below), whose sum is σ = 9139430286. Its totient is φ = 5463794736.

The previous prime is 7212781789. The next prime is 7212781841. The reversal of 7212781805 is 5081872127.

7212781805 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 5770225444 + 1442556361 = 75962^2 + 37981^2 .

It is not a de Polignac number, because 7212781805 - 2⁴ = 7212781789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 3607196 + ... + 3609194.

It is an arithmetic number, because the mean of its divisors is an integer number (507746127).

Almost surely, 2^7212781805 is an apocalyptic number.

It is an amenable number.

7212781805 is a deficient number, since it is larger than the sum of its proper divisors (1926648481).

7212781805 is an frugal number, since it uses more digits than its factorization.

7212781805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4041 (or 2023 counting only the distinct ones).

The product of its (nonzero) digits is 62720, while the sum is 41.

The square root of 7212781805 is about 84928.0978534195. The cubic root of 7212781805 is about 1932.1207508434.

Multiplying 7212781805 by its product of nonzero digits (62720), we get a square (452385674809600 = 21269360²).

The spelling of 7212781805 in words is "seven billion, two hundred twelve million, seven hundred eighty-one thousand, eight hundred five".