815781649 has 2 divisors, whose sum is σ = 815781650. Its totient is φ = 815781648.

The previous prime is 815781619. The next prime is 815781677. The reversal of 815781649 is 946187518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 566773249 + 249008400 = 23807^2 + 15780^2 .

It is a cyclic number.

It is not a de Polignac number, because 815781649 - 2¹⁵ = 815748881 is a prime.

It is not a weakly prime, because it can be changed into another prime (815781619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407890824 + 407890825.

It is an arithmetic number, because the mean of its divisors is an integer number (407890825).

Almost surely, 2^815781649 is an apocalyptic number.

It is an amenable number.

815781649 is a deficient number, since it is larger than the sum of its proper divisors (1).

815781649 is an equidigital number, since it uses as much as digits as its factorization.

815781649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 483840, while the sum is 49.

The square root of 815781649 is about 28561.8915515062. The cubic root of 815781649 is about 934.3823879372.

The spelling of 815781649 in words is "eight hundred fifteen million, seven hundred eighty-one thousand, six hundred forty-nine".