16978981 has 2 divisors, whose sum is σ = 16978982. Its totient is φ = 16978980.

The previous prime is 16978957. The next prime is 16978999. The reversal of 16978981 is 18987961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15132100 + 1846881 = 3890^2 + 1359^2 .

It is a cyclic number.

It is not a de Polignac number, because 16978981 - 2¹⁵ = 16946213 is a prime.

It is a super-2 number, since 2×16978981² = 576571591596722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16978901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8489490 + 8489491.

It is an arithmetic number, because the mean of its divisors is an integer number (8489491).

Almost surely, 2^16978981 is an apocalyptic number.

It is an amenable number.

16978981 is a deficient number, since it is larger than the sum of its proper divisors (1).

16978981 is an equidigital number, since it uses as much as digits as its factorization.

16978981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 217728, while the sum is 49.

The square root of 16978981 is about 4120.5559090977. Note that the first 3 decimals coincide. The cubic root of 16978981 is about 257.0221432671.

The spelling of 16978981 in words is "sixteen million, nine hundred seventy-eight thousand, nine hundred eighty-one".