999551 has 6 divisors (see below), whose sum is σ = 1162800. Its totient is φ = 856716.

The previous prime is 999541. The next prime is 999553. The reversal of 999551 is 155999.

It is not a de Polignac number, because 999551 - 2¹⁰ = 998527 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 999551.

It is not an unprimeable number, because it can be changed into a prime (999553) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10151 + ... + 10248.

It is an arithmetic number, because the mean of its divisors is an integer number (193800).

2⁹⁹⁹⁵⁵¹ is an apocalyptic number.

999551 is a deficient number, since it is larger than the sum of its proper divisors (163249).

999551 is a wasteful number, since it uses less digits than its factorization.

999551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20413 (or 20406 counting only the distinct ones).

The product of its digits is 18225, while the sum is 38.

The square root of 999551 is about 999.7754747942. The cubic root of 999551 is about 99.9850310928.

It can be divided in two parts, 99 and 9551, that multiplied together give a palindrome (945549).

The spelling of 999551 in words is "nine hundred ninety-nine thousand, five hundred fifty-one".