21355853 has 4 divisors (see below), whose sum is σ = 21449340. Its totient is φ = 21262368.

The previous prime is 21355849. The next prime is 21355883. The reversal of 21355853 is 35855312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20268004 + 1087849 = 4502^2 + 1043^2 .

It is a cyclic number.

It is not a de Polignac number, because 21355853 - 2² = 21355849 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 (21355823) 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, 46400 + ... + 46857.

It is an arithmetic number, because the mean of its divisors is an integer number (5362335).

Almost surely, 2^21355853 is an apocalyptic number.

It is an amenable number.

21355853 is a deficient number, since it is larger than the sum of its proper divisors (93487).

21355853 is an equidigital number, since it uses as much as digits as its factorization.

21355853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93486.

The product of its digits is 18000, while the sum is 32.

The square root of 21355853 is about 4621.2393359358. The cubic root of 21355853 is about 277.4420645766.

The spelling of 21355853 in words is "twenty-one million, three hundred fifty-five thousand, eight hundred fifty-three".