16553981 has 2 divisors, whose sum is σ = 16553982. Its totient is φ = 16553980.

The previous prime is 16553941. The next prime is 16553989. The reversal of 16553981 is 18935561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11222500 + 5331481 = 3350^2 + 2309^2 .

It is a cyclic number.

It is not a de Polignac number, because 16553981 - 2¹⁸ = 16291837 is a prime.

It is a super-2 number, since 2×16553981² = 548068573896722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16553989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8276990 + 8276991.

It is an arithmetic number, because the mean of its divisors is an integer number (8276991).

Almost surely, 2^16553981 is an apocalyptic number.

It is an amenable number.

16553981 is a deficient number, since it is larger than the sum of its proper divisors (1).

16553981 is an equidigital number, since it uses as much as digits as its factorization.

16553981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32400, while the sum is 38.

The square root of 16553981 is about 4068.6583783847. The cubic root of 16553981 is about 254.8594945550.

The spelling of 16553981 in words is "sixteen million, five hundred fifty-three thousand, nine hundred eighty-one".