816551 has 4 divisors (see below), whose sum is σ = 819312. Its totient is φ = 813792.

The previous prime is 816547. The next prime is 816559. The reversal of 816551 is 155618.

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 816551 - 2² = 816547 is a prime.

It is a super-3 number, since 3×816551³ = 1633319698051596453, which contains 333 as substring.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 816551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816559) 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, 875 + ... + 1548.

It is an arithmetic number, because the mean of its divisors is an integer number (204828).

2⁸¹⁶⁵⁵¹ is an apocalyptic number.

816551 is a deficient number, since it is larger than the sum of its proper divisors (2761).

816551 is a wasteful number, since it uses less digits than its factorization.

816551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2760.

The product of its digits is 1200, while the sum is 26.

The square root of 816551 is about 903.6321154098. The cubic root of 816551 is about 93.4676029485.

The spelling of 816551 in words is "eight hundred sixteen thousand, five hundred fifty-one".