21088890 has 64 divisors (see below), whose sum is σ = 57784320. Its totient is φ = 5469120.

The previous prime is 21088871. The next prime is 21088909. The reversal of 21088890 is 9888012.

It is an interprime number because it is at equal distance from previous prime (21088871) and next prime (21088909).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8935 + ... + 11045.

It is an arithmetic number, because the mean of its divisors is an integer number (902880).

Almost surely, 2^21088890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21088890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28892160).

21088890 is an abundant number, since it is smaller than the sum of its proper divisors (36695430).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21088890 is a wasteful number, since it uses less digits than its factorization.

21088890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2164 (or 2158 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 21088890 is about 4592.2641474549. The cubic root of 21088890 is about 276.2811407467.

The spelling of 21088890 in words is "twenty-one million, eighty-eight thousand, eight hundred ninety".