21053261 has 4 divisors (see below), whose sum is σ = 21062592. Its totient is φ = 21043932.

The previous prime is 21053203. The next prime is 21053267. The reversal of 21053261 is 16235012.

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 21053261 - 2¹⁴ = 21036877 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 (21053267) 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, 1070 + ... + 6576.

It is an arithmetic number, because the mean of its divisors is an integer number (5265648).

Almost surely, 2^21053261 is an apocalyptic number.

It is an amenable number.

21053261 is a deficient number, since it is larger than the sum of its proper divisors (9331).

21053261 is an equidigital number, since it uses as much as digits as its factorization.

21053261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9330.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21053261 is about 4588.3832664676. The cubic root of 21053261 is about 276.1254636822.

Adding to 21053261 its reverse (16235012), we get a palindrome (37288273).

The spelling of 21053261 in words is "twenty-one million, fifty-three thousand, two hundred sixty-one".