816537421 has 54 divisors (see below), whose sum is σ = 1064464170. Its totient is φ = 624298752.

The previous prime is 816537391. The next prime is 816537431. The reversal of 816537421 is 124735618.

It can be written as a sum of positive squares in 3 ways, for example, as 411521796 + 405015625 = 20286^2 + 20125^2 .

It is not a de Polignac number, because 816537421 - 2⁵ = 816537389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816537431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 7491115 + ... + 7491223.

Almost surely, 2^816537421 is an apocalyptic number.

It is an amenable number.

816537421 is a deficient number, since it is larger than the sum of its proper divisors (247926749).

816537421 is a wasteful number, since it uses less digits than its factorization.

816537421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203 (or 156 counting only the distinct ones).

The product of its digits is 40320, while the sum is 37.

The square root of 816537421 is about 28575.1189148882. The cubic root of 816537421 is about 934.6708483284.

The spelling of 816537421 in words is "eight hundred sixteen million, five hundred thirty-seven thousand, four hundred twenty-one".