21635573 has 4 divisors (see below), whose sum is σ = 21958560. Its totient is φ = 21312588.

The previous prime is 21635563. The next prime is 21635587. The reversal of 21635573 is 37553612.

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 21635573 - 2¹⁰ = 21634549 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 (21635503) 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, 161393 + ... + 161526.

It is an arithmetic number, because the mean of its divisors is an integer number (5489640).

Almost surely, 2^21635573 is an apocalyptic number.

It is an amenable number.

21635573 is a deficient number, since it is larger than the sum of its proper divisors (322987).

21635573 is an equidigital number, since it uses as much as digits as its factorization.

21635573 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322986.

The product of its digits is 18900, while the sum is 32.

The square root of 21635573 is about 4651.4054865170. The cubic root of 21635573 is about 278.6481306462.

The spelling of 21635573 in words is "twenty-one million, six hundred thirty-five thousand, five hundred seventy-three".