816521649 has 4 divisors (see below), whose sum is σ = 1088695536. Its totient is φ = 544347764.

The previous prime is 816521623. The next prime is 816521659. The reversal of 816521649 is 946125618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 816521649 - 2¹¹ = 816519601 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 816521649.

It is not an unprimeable number, because it can be changed into a prime (816521609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136086939 + ... + 136086944.

It is an arithmetic number, because the mean of its divisors is an integer number (272173884).

Almost surely, 2^816521649 is an apocalyptic number.

It is an amenable number.

816521649 is a deficient number, since it is larger than the sum of its proper divisors (272173887).

816521649 is a wasteful number, since it uses less digits than its factorization.

816521649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272173886.

The product of its digits is 103680, while the sum is 42.

The square root of 816521649 is about 28574.8429392009. The cubic root of 816521649 is about 934.6648303460.

The spelling of 816521649 in words is "eight hundred sixteen million, five hundred twenty-one thousand, six hundred forty-nine".