21031889 has 6 divisors (see below), whose sum is σ = 21491154. Its totient is φ = 20582240.

The previous prime is 21031883. The next prime is 21031909. The reversal of 21031889 is 98813012.

It can be written as a sum of positive squares in only one way, i.e., 17497489 + 3534400 = 4183^2 + 1880^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21031889 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031883) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2552 + ... + 6969.

It is an arithmetic number, because the mean of its divisors is an integer number (3581859).

Almost surely, 2^21031889 is an apocalyptic number.

It is an amenable number.

21031889 is a deficient number, since it is larger than the sum of its proper divisors (459265).

21031889 is an frugal number, since it uses more digits than its factorization.

21031889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9615 (or 9568 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 21031889 is about 4586.0537502301. The cubic root of 21031889 is about 276.0319967456.

The spelling of 21031889 in words is "twenty-one million, thirty-one thousand, eight hundred eighty-nine".