15891121 has 2 divisors, whose sum is σ = 15891122. Its totient is φ = 15891120.

The previous prime is 15891103. The next prime is 15891133. The reversal of 15891121 is 12119851.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10962721 + 4928400 = 3311^2 + 2220^2 .

It is a cyclic number.

It is not a de Polignac number, because 15891121 - 2¹³ = 15882929 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 15891121.

It is not a weakly prime, because it can be changed into another prime (15891181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7945560 + 7945561.

It is an arithmetic number, because the mean of its divisors is an integer number (7945561).

Almost surely, 2^15891121 is an apocalyptic number.

It is an amenable number.

15891121 is a deficient number, since it is larger than the sum of its proper divisors (1).

15891121 is an equidigital number, since it uses as much as digits as its factorization.

15891121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 28.

The square root of 15891121 is about 3986.3668922968. The cubic root of 15891121 is about 251.4113296022.

It can be divided in two parts, 15 and 891121, that added together give a square (891136 = 944²).

The spelling of 15891121 in words is "fifteen million, eight hundred ninety-one thousand, one hundred twenty-one".