16001681 has 2 divisors, whose sum is σ = 16001682. Its totient is φ = 16001680.

The previous prime is 16001663. The next prime is 16001683. The reversal of 16001681 is 18610061.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16000000 + 1681 = 4000^2 + 41^2 .

It is an emirp because it is prime and its reverse (18610061) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16001681 is a prime.

It is a super-2 number, since 2×16001681² = 512107589651522, which contains 22 as substring.

Together with 16001683, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16001683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8000840 + 8000841.

It is an arithmetic number, because the mean of its divisors is an integer number (8000841).

Almost surely, 2^16001681 is an apocalyptic number.

It is an amenable number.

16001681 is a deficient number, since it is larger than the sum of its proper divisors (1).

16001681 is an equidigital number, since it uses as much as digits as its factorization.

16001681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 16001681 is about 4000.2101194812. The cubic root of 16001681 is about 251.9930343670.

It can be divided in two parts, 1600 and 1681, that multiplied together give a square (2689600 = 1640²).

The spelling of 16001681 in words is "sixteen million, one thousand, six hundred eighty-one".