21090889 has 2 divisors, whose sum is σ = 21090890. Its totient is φ = 21090888.

The previous prime is 21090871. The next prime is 21090899. The reversal of 21090889 is 98809012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20250000 + 840889 = 4500^2 + 917^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21090889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21090809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10545444 + 10545445.

It is an arithmetic number, because the mean of its divisors is an integer number (10545445).

Almost surely, 2^21090889 is an apocalyptic number.

It is an amenable number.

21090889 is a deficient number, since it is larger than the sum of its proper divisors (1).

21090889 is an equidigital number, since it uses as much as digits as its factorization.

21090889 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 37.

The square root of 21090889 is about 4592.4817909274. The cubic root of 21090889 is about 276.2898699646.

The spelling of 21090889 in words is "twenty-one million, ninety thousand, eight hundred eighty-nine".