816515551 has 4 divisors (see below), whose sum is σ = 817218792. Its totient is φ = 815812312.

The previous prime is 816515543. The next prime is 816515591. The reversal of 816515551 is 155515618.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 816515551 - 2³ = 816515543 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 816515551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816515501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 349876 + ... + 352201.

It is an arithmetic number, because the mean of its divisors is an integer number (204304698).

Almost surely, 2^816515551 is an apocalyptic number.

816515551 is a deficient number, since it is larger than the sum of its proper divisors (703241).

816515551 is a wasteful number, since it uses less digits than its factorization.

816515551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 703240.

The product of its digits is 30000, while the sum is 37.

The square root of 816515551 is about 28574.7362367529. The cubic root of 816515551 is about 934.6625035653.

It can be divided in two parts, 8165 and 15551, that added together give a square (23716 = 154²).

The spelling of 816515551 in words is "eight hundred sixteen million, five hundred fifteen thousand, five hundred fifty-one".