16603981 has 2 divisors, whose sum is σ = 16603982. Its totient is φ = 16603980.

The previous prime is 16603969. The next prime is 16603987. The reversal of 16603981 is 18930661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15139881 + 1464100 = 3891^2 + 1210^2 .

It is an emirp because it is prime and its reverse (18930661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16603981 - 2⁵ = 16603949 is a prime.

It is a super-2 number, since 2×16603981² = 551384370096722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16603987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8301990 + 8301991.

It is an arithmetic number, because the mean of its divisors is an integer number (8301991).

Almost surely, 2^16603981 is an apocalyptic number.

It is an amenable number.

16603981 is a deficient number, since it is larger than the sum of its proper divisors (1).

16603981 is an equidigital number, since it uses as much as digits as its factorization.

16603981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 16603981 is about 4074.7982772157. The cubic root of 16603981 is about 255.1158310115.

The spelling of 16603981 in words is "sixteen million, six hundred three thousand, nine hundred eighty-one".