16989821 has 2 divisors, whose sum is σ = 16989822. Its totient is φ = 16989820.

The previous prime is 16989799. The next prime is 16989823. The reversal of 16989821 is 12898961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8637721 + 8352100 = 2939^2 + 2890^2 .

It is a cyclic number.

It is not a de Polignac number, because 16989821 - 2⁶ = 16989757 is a prime.

It is a super-2 number, since 2×16989821² = 577308035224082, which contains 22 as substring.

Together with 16989823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16989823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8494910 + 8494911.

It is an arithmetic number, because the mean of its divisors is an integer number (8494911).

Almost surely, 2^16989821 is an apocalyptic number.

It is an amenable number.

16989821 is a deficient number, since it is larger than the sum of its proper divisors (1).

16989821 is an equidigital number, since it uses as much as digits as its factorization.

16989821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 44.

The square root of 16989821 is about 4121.8710557221. The cubic root of 16989821 is about 257.0768290641.

The spelling of 16989821 in words is "sixteen million, nine hundred eighty-nine thousand, eight hundred twenty-one".