21938261 has 4 divisors (see below), whose sum is σ = 21948000. Its totient is φ = 21928524.

The previous prime is 21938249. The next prime is 21938269. The reversal of 21938261 is 16283912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21938261 - 2⁶ = 21938197 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 (21938269) 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, 440 + ... + 6638.

It is an arithmetic number, because the mean of its divisors is an integer number (5487000).

Almost surely, 2^21938261 is an apocalyptic number.

It is an amenable number.

21938261 is a deficient number, since it is larger than the sum of its proper divisors (9739).

21938261 is an equidigital number, since it uses as much as digits as its factorization.

21938261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9738.

The product of its digits is 5184, while the sum is 32.

The square root of 21938261 is about 4683.8297364443. The cubic root of 21938261 is about 279.9415736937.

The spelling of 21938261 in words is "twenty-one million, nine hundred thirty-eight thousand, two hundred sixty-one".