21652261 has 4 divisors (see below), whose sum is σ = 21691692. Its totient is φ = 21612832.

The previous prime is 21652219. The next prime is 21652273. The reversal of 21652261 is 16225612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13184161 + 8468100 = 3631^2 + 2910^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21652261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21652201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18880 + ... + 19993.

It is an arithmetic number, because the mean of its divisors is an integer number (5422923).

Almost surely, 2^21652261 is an apocalyptic number.

It is an amenable number.

21652261 is a deficient number, since it is larger than the sum of its proper divisors (39431).

21652261 is an equidigital number, since it uses as much as digits as its factorization.

21652261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39430.

The product of its digits is 1440, while the sum is 25.

The square root of 21652261 is about 4653.1990071348. The cubic root of 21652261 is about 278.7197547402.

Adding to 21652261 its reverse (16225612), we get a palindrome (37877873).

It can be divided in two parts, 216 and 52261, that multiplied together give a triangular number (11288376 = T₄₇₅₁).

The spelling of 21652261 in words is "twenty-one million, six hundred fifty-two thousand, two hundred sixty-one".