21049261 has 4 divisors (see below), whose sum is σ = 21058524. Its totient is φ = 21040000.

The previous prime is 21049243. The next prime is 21049271. The reversal of 21049261 is 16294012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 7128900 + 13920361 = 2670^2 + 3731^2 .

It is a cyclic number.

It is not a de Polignac number, because 21049261 - 2¹⁷ = 20918189 is a prime.

It is a super-2 number, since 2×21049261² = 886142777292242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21049201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1371 + ... + 6631.

It is an arithmetic number, because the mean of its divisors is an integer number (5264631).

Almost surely, 2^21049261 is an apocalyptic number.

It is an amenable number.

21049261 is a deficient number, since it is larger than the sum of its proper divisors (9263).

21049261 is an equidigital number, since it uses as much as digits as its factorization.

21049261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9262.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21049261 is about 4587.9473623833. The cubic root of 21049261 is about 276.1079751514.

The spelling of 21049261 in words is "twenty-one million, forty-nine thousand, two hundred sixty-one".