18687481 has 2 divisors, whose sum is σ = 18687482. Its totient is φ = 18687480.

The previous prime is 18687463. The next prime is 18687491. The reversal of 18687481 is 18478681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12362256 + 6325225 = 3516^2 + 2515^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18687481 is a prime.

It is a super-2 number, since 2×18687481² = 698443892250722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18687401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9343740 + 9343741.

It is an arithmetic number, because the mean of its divisors is an integer number (9343741).

Almost surely, 2^18687481 is an apocalyptic number.

It is an amenable number.

18687481 is a deficient number, since it is larger than the sum of its proper divisors (1).

18687481 is an equidigital number, since it uses as much as digits as its factorization.

18687481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 86016, while the sum is 43.

The square root of 18687481 is about 4322.9019188503. The cubic root of 18687481 is about 265.3690408344.

The spelling of 18687481 in words is "eighteen million, six hundred eighty-seven thousand, four hundred eighty-one".