16381661 has 2 divisors, whose sum is σ = 16381662. Its totient is φ = 16381660.

The previous prime is 16381657. The next prime is 16381691. The reversal of 16381661 is 16618361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14707225 + 1674436 = 3835^2 + 1294^2 .

It is a cyclic number.

It is not a de Polignac number, because 16381661 - 2² = 16381657 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16381601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8190830 + 8190831.

It is an arithmetic number, because the mean of its divisors is an integer number (8190831).

Almost surely, 2^16381661 is an apocalyptic number.

It is an amenable number.

16381661 is a deficient number, since it is larger than the sum of its proper divisors (1).

16381661 is an equidigital number, since it uses as much as digits as its factorization.

16381661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 32.

The square root of 16381661 is about 4047.4264662869. The cubic root of 16381661 is about 253.9720813756.

The spelling of 16381661 in words is "sixteen million, three hundred eighty-one thousand, six hundred sixty-one".