161901686437 has 2 divisors, whose sum is σ = 161901686438. Its totient is φ = 161901686436.

The previous prime is 161901686369. The next prime is 161901686473. The reversal of 161901686437 is 734686109161.

Together with next prime (161901686473) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 90633510916 + 71268175521 = 301054^2 + 266961^2 .

It is a cyclic number.

It is not a de Polignac number, because 161901686437 - 2³¹ = 159754202789 is a prime.

It is a super-2 number, since 2×161901686437² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161901681437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80950843218 + 80950843219.

It is an arithmetic number, because the mean of its divisors is an integer number (80950843219).

Almost surely, 2^161901686437 is an apocalyptic number.

It is an amenable number.

161901686437 is a deficient number, since it is larger than the sum of its proper divisors (1).

161901686437 is an equidigital number, since it uses as much as digits as its factorization.

161901686437 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1306368, while the sum is 52.

The spelling of 161901686437 in words is "one hundred sixty-one billion, nine hundred one million, six hundred eighty-six thousand, four hundred thirty-seven".