21809053 has 4 divisors (see below), whose sum is σ = 24924640. Its totient is φ = 18693468.

The previous prime is 21809009. The next prime is 21809057. The reversal of 21809053 is 35090812.

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.

It is a cyclic number.

It is not a de Polignac number, because 21809053 - 2⁹ = 21808541 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 (21809057) 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, 1557783 + ... + 1557796.

It is an arithmetic number, because the mean of its divisors is an integer number (6231160).

Almost surely, 2^21809053 is an apocalyptic number.

It is an amenable number.

21809053 is a deficient number, since it is larger than the sum of its proper divisors (3115587).

21809053 is an equidigital number, since it uses as much as digits as its factorization.

21809053 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3115586.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21809053 is about 4670.0163811276. The cubic root of 21809053 is about 279.3909081289.

Adding to 21809053 its reverse (35090812), we get a palindrome (56899865).

The spelling of 21809053 in words is "twenty-one million, eight hundred nine thousand, fifty-three".