16388981 has 12 divisors (see below), whose sum is σ = 19174572. Its totient is φ = 13966848.

The previous prime is 16388951. The next prime is 16388989. The reversal of 16388981 is 18988361.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5564881 + 10824100 = 2359^2 + 3290^2 .

It is not a de Polignac number, because 16388981 - 2⁶ = 16388917 is a prime.

It is a super-2 number, since 2×16388981² = 537197396436722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16388989) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8591 + ... + 10323.

It is an arithmetic number, because the mean of its divisors is an integer number (1597881).

Almost surely, 2^16388981 is an apocalyptic number.

It is an amenable number.

16388981 is a deficient number, since it is larger than the sum of its proper divisors (2785591).

16388981 is a wasteful number, since it uses less digits than its factorization.

16388981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1940 (or 1933 counting only the distinct ones).

The product of its digits is 82944, while the sum is 44.

The square root of 16388981 is about 4048.3306436110. The cubic root of 16388981 is about 254.0099041336.

The spelling of 16388981 in words is "sixteen million, three hundred eighty-eight thousand, nine hundred eighty-one".