21028590 has 72 divisors (see below), whose sum is σ = 60127704. Its totient is φ = 5095200.

The previous prime is 21028549. The next prime is 21028597. The reversal of 21028590 is 9582012.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21028597) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 9925 + ... + 11855.

It is an arithmetic number, because the mean of its divisors is an integer number (835107).

Almost surely, 2^21028590 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21028590, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30063852).

21028590 is an abundant number, since it is smaller than the sum of its proper divisors (39099114).

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

21028590 is a wasteful number, since it uses less digits than its factorization.

21028590 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1966 (or 1952 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 21028590 is about 4585.6940587004. The cubic root of 21028590 is about 276.0175634696.

The spelling of 21028590 in words is "twenty-one million, twenty-eight thousand, five hundred ninety".