15981557 has 2 divisors, whose sum is σ = 15981558. Its totient is φ = 15981556.

The previous prime is 15981541. The next prime is 15981593. The reversal of 15981557 is 75518951.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14638276 + 1343281 = 3826^2 + 1159^2 .

It is an emirp because it is prime and its reverse (75518951) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15981557 - 2⁴ = 15981541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15981157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7990778 + 7990779.

It is an arithmetic number, because the mean of its divisors is an integer number (7990779).

Almost surely, 2^15981557 is an apocalyptic number.

It is an amenable number.

15981557 is a deficient number, since it is larger than the sum of its proper divisors (1).

15981557 is an equidigital number, since it uses as much as digits as its factorization.

15981557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63000, while the sum is 41.

The square root of 15981557 is about 3997.6939602726. The cubic root of 15981557 is about 251.8873530712.

The spelling of 15981557 in words is "fifteen million, nine hundred eighty-one thousand, five hundred fifty-seven".