21445866 has 48 divisors (see below), whose sum is σ = 51413544. Its totient is φ = 6417792.

The previous prime is 21445861. The next prime is 21445871. The reversal of 21445866 is 66854412.

It is an interprime number because it is at equal distance from previous prime (21445861) and next prime (21445871).

It can be written as a sum of positive squares in 4 ways, for example, as 18792225 + 2653641 = 4335^2 + 1629^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21445866.

It is not an unprimeable number, because it can be changed into a prime (21445861) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7420 + ... + 9896.

Almost surely, 2^21445866 is an apocalyptic number.

21445866 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21445866, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25706772).

21445866 is an abundant number, since it is smaller than the sum of its proper divisors (29967678).

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

21445866 is a wasteful number, since it uses less digits than its factorization.

21445866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2535 (or 2532 counting only the distinct ones).

The product of its digits is 46080, while the sum is 36.

The square root of 21445866 is about 4630.9681493182. The cubic root of 21445866 is about 277.8313159857.

The spelling of 21445866 in words is "twenty-one million, four hundred forty-five thousand, eight hundred sixty-six".