21545291 has 4 divisors (see below), whose sum is σ = 21555792. Its totient is φ = 21534792.

The previous prime is 21545263. The next prime is 21545309. The reversal of 21545291 is 19254512.

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 is a cyclic number.

It is not a de Polignac number, because 21545291 - 2¹⁸ = 21283147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21545201) 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, 1055 + ... + 6648.

It is an arithmetic number, because the mean of its divisors is an integer number (5388948).

Almost surely, 2^21545291 is an apocalyptic number.

21545291 is a deficient number, since it is larger than the sum of its proper divisors (10501).

21545291 is an equidigital number, since it uses as much as digits as its factorization.

21545291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10500.

The product of its digits is 3600, while the sum is 29.

The square root of 21545291 is about 4641.6905325538. The cubic root of 21545291 is about 278.2600046668.

The spelling of 21545291 in words is "twenty-one million, five hundred forty-five thousand, two hundred ninety-one".