21440621 has 6 divisors (see below), whose sum is σ = 22776330. Its totient is φ = 20179136.

The previous prime is 21440609. The next prime is 21440647. The reversal of 21440621 is 12604412.

It can be written as a sum of positive squares in 3 ways, for example, as 6916900 + 14523721 = 2630^2 + 3811^2 .

It is not a de Polignac number, because 21440621 - 2¹⁸ = 21178477 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21440593 and 21440602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21440681) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36806 + ... + 37383.

It is an arithmetic number, because the mean of its divisors is an integer number (3796055).

Almost surely, 2^21440621 is an apocalyptic number.

It is an amenable number.

21440621 is a deficient number, since it is larger than the sum of its proper divisors (1335709).

21440621 is an equidigital number, since it uses as much as digits as its factorization.

21440621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74223 (or 74206 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21440621 is about 4630.4018184171. The cubic root of 21440621 is about 277.8086644707.

The spelling of 21440621 in words is "twenty-one million, four hundred forty thousand, six hundred twenty-one".