21098989 has 8 divisors (see below), whose sum is σ = 22466808. Its totient is φ = 19745280.

The previous prime is 21098951. The next prime is 21099007. The reversal of 21098989 is 98989012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 469225 + 20629764 = 685^2 + 4542^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21098989 - 2¹¹ = 21096941 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21098089) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 352 + ... + 6505.

It is an arithmetic number, because the mean of its divisors is an integer number (2808351).

Almost surely, 2^21098989 is an apocalyptic number.

It is an amenable number.

21098989 is a deficient number, since it is larger than the sum of its proper divisors (1367819).

21098989 is a wasteful number, since it uses less digits than its factorization.

21098989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7055.

The product of its (nonzero) digits is 93312, while the sum is 46.

The square root of 21098989 is about 4593.3635823871. The cubic root of 21098989 is about 276.3252353383.

It can be divided in two parts, 210 and 98989, that added together give a palindrome (99199).

The spelling of 21098989 in words is "twenty-one million, ninety-eight thousand, nine hundred eighty-nine".