161215201531 has 2 divisors, whose sum is σ = 161215201532. Its totient is φ = 161215201530.

The previous prime is 161215201513. The next prime is 161215201579. The reversal of 161215201531 is 135102512161.

Together with previous prime (161215201513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is an emirp because it is prime and its reverse (135102512161) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161215201531 is a prime.

It is a super-2 number, since 2×161215201531² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 161215201531.

It is not a weakly prime, because it can be changed into another prime (161215201331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80607600765 + 80607600766.

It is an arithmetic number, because the mean of its divisors is an integer number (80607600766).

Almost surely, 2^161215201531 is an apocalyptic number.

161215201531 is a deficient number, since it is larger than the sum of its proper divisors (1).

161215201531 is an equidigital number, since it uses as much as digits as its factorization.

161215201531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1800, while the sum is 28.

Adding to 161215201531 its reverse (135102512161), we get a palindrome (296317713692).

The spelling of 161215201531 in words is "one hundred sixty-one billion, two hundred fifteen million, two hundred one thousand, five hundred thirty-one".