21262290 has 64 divisors (see below), whose sum is σ = 58945536. Its totient is φ = 4807872.

The previous prime is 21262289. The next prime is 21262301. The reversal of 21262290 is 9226212.

It is a self number, because there is not a number n which added to its sum of digits gives 21262290.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 21139 + ... + 22121.

It is an arithmetic number, because the mean of its divisors is an integer number (921024).

Almost surely, 2^21262290 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21262290, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29472768).

21262290 is an abundant number, since it is smaller than the sum of its proper divisors (37683246).

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

21262290 is a wasteful number, since it uses less digits than its factorization.

21262290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1103.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21262290 is about 4611.1050736239. The cubic root of 21262290 is about 277.0363005075.

The spelling of 21262290 in words is "twenty-one million, two hundred sixty-two thousand, two hundred ninety".