21308641 has 4 divisors (see below), whose sum is σ = 21391812. Its totient is φ = 21225472.

The previous prime is 21308629. The next prime is 21308653. The reversal of 21308641 is 14680312.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21308629) and next prime (21308653).

It can be written as a sum of positive squares in 2 ways, for example, as 14470416 + 6838225 = 3804^2 + 2615^2 .

It is a cyclic number.

It is not a de Polignac number, because 21308641 - 2¹⁵ = 21275873 is a prime.

It is a super-3 number, since 3×21308641³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21308611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41200 + ... + 41713.

It is an arithmetic number, because the mean of its divisors is an integer number (5347953).

Almost surely, 2^21308641 is an apocalyptic number.

It is an amenable number.

21308641 is a deficient number, since it is larger than the sum of its proper divisors (83171).

21308641 is an equidigital number, since it uses as much as digits as its factorization.

21308641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83170.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21308641 is about 4616.1283561010. The cubic root of 21308641 is about 277.2374640063.

Adding to 21308641 its reverse (14680312), we get a palindrome (35988953).

The spelling of 21308641 in words is "twenty-one million, three hundred eight thousand, six hundred forty-one".