20171881505987 has 2 divisors, whose sum is σ = 20171881505988. Its totient is φ = 20171881505986.

The previous prime is 20171881505953. The next prime is 20171881506031. The reversal of 20171881505987 is 78950518817102.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20171881505987 - 2¹⁰ = 20171881504963 is a prime.

It is not a weakly prime, because it can be changed into another prime (20171881505947) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10085940752993 + 10085940752994.

It is an arithmetic number, because the mean of its divisors is an integer number (10085940752994).

Almost surely, 2^{20171881505987} is an apocalyptic number.

20171881505987 is a deficient number, since it is larger than the sum of its proper divisors (1).

20171881505987 is an equidigital number, since it uses as much as digits as its factorization.

20171881505987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11289600, while the sum is 62.

The spelling of 20171881505987 in words is "twenty trillion, one hundred seventy-one billion, eight hundred eighty-one million, five hundred five thousand, nine hundred eighty-seven".