15551231 has 2 divisors, whose sum is σ = 15551232. Its totient is φ = 15551230.

The previous prime is 15551213. The next prime is 15551233. The reversal of 15551231 is 13215551.

It is a happy number.

Together with previous prime (15551213) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 15551231 - 2¹⁴ = 15534847 is a prime.

It is a super-2 number, since 2×15551231² = 483681571230722, which contains 22 as substring.

Together with 15551233, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 15551197 and 15551206.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15551233) 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 as a sum of consecutive naturals, namely, 7775615 + 7775616.

It is an arithmetic number, because the mean of its divisors is an integer number (7775616).

Almost surely, 2^15551231 is an apocalyptic number.

15551231 is a deficient number, since it is larger than the sum of its proper divisors (1).

15551231 is an equidigital number, since it uses as much as digits as its factorization.

15551231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 750, while the sum is 23.

The square root of 15551231 is about 3943.5049131452. The cubic root of 15551231 is about 249.6059445409.

Adding to 15551231 its reverse (13215551), we get a palindrome (28766782).

The spelling of 15551231 in words is "fifteen million, five hundred fifty-one thousand, two hundred thirty-one".