17991551 has 2 divisors, whose sum is σ = 17991552. Its totient is φ = 17991550.

The previous prime is 17991541. The next prime is 17991557. The reversal of 17991551 is 15519971.

It is a strong prime.

It is an emirp because it is prime and its reverse (15519971) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 17991551 - 2⁶ = 17991487 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (17991557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8995775 + 8995776.

It is an arithmetic number, because the mean of its divisors is an integer number (8995776).

Almost surely, 2^17991551 is an apocalyptic number.

17991551 is a deficient number, since it is larger than the sum of its proper divisors (1).

17991551 is an equidigital number, since it uses as much as digits as its factorization.

17991551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14175, while the sum is 38.

The square root of 17991551 is about 4241.6448460473. The cubic root of 17991551 is about 262.0331281071.

The spelling of 17991551 in words is "seventeen million, nine hundred ninety-one thousand, five hundred fifty-one".