15217991 has 2 divisors, whose sum is σ = 15217992. Its totient is φ = 15217990.

The previous prime is 15217963. The next prime is 15217997. The reversal of 15217991 is 19971251.

15217991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is an emirp because it is prime and its reverse (19971251) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15217991 - 2¹⁴ = 15201607 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15217997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7608995 + 7608996.

It is an arithmetic number, because the mean of its divisors is an integer number (7608996).

Almost surely, 2^15217991 is an apocalyptic number.

15217991 is a deficient number, since it is larger than the sum of its proper divisors (1).

15217991 is an equidigital number, since it uses as much as digits as its factorization.

15217991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5670, while the sum is 35.

The square root of 15217991 is about 3901.0243526541. The cubic root of 15217991 is about 247.8101597380.

The spelling of 15217991 in words is "fifteen million, two hundred seventeen thousand, nine hundred ninety-one".