21355473 has 4 divisors (see below), whose sum is σ = 28473968. Its totient is φ = 14236980.

The previous prime is 21355471. The next prime is 21355483. The reversal of 21355473 is 37455312.

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 not a de Polignac number, because 21355473 - 2¹ = 21355471 is a prime.

It is a super-3 number, since 3×21355473³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21355473.

It is not an unprimeable number, because it can be changed into a prime (21355471) 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, 3559243 + ... + 3559248.

It is an arithmetic number, because the mean of its divisors is an integer number (7118492).

Almost surely, 2^21355473 is an apocalyptic number.

It is an amenable number.

21355473 is a deficient number, since it is larger than the sum of its proper divisors (7118495).

21355473 is an equidigital number, since it uses as much as digits as its factorization.

21355473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7118494.

The product of its digits is 12600, while the sum is 30.

The square root of 21355473 is about 4621.1982212409. The cubic root of 21355473 is about 277.4404189916.

The spelling of 21355473 in words is "twenty-one million, three hundred fifty-five thousand, four hundred seventy-three".