21555321 has 8 divisors (see below), whose sum is σ = 28763904. Its totient is φ = 14358480.

The previous prime is 21555311. The next prime is 21555353. The reversal of 21555321 is 12355512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21555321 - 2⁹ = 21554809 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21555291 and 21555300.

It is not an unprimeable number, because it can be changed into a prime (21555311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3160 + ... + 7286.

It is an arithmetic number, because the mean of its divisors is an integer number (3595488).

Almost surely, 2^21555321 is an apocalyptic number.

It is an amenable number.

21555321 is a deficient number, since it is larger than the sum of its proper divisors (7208583).

21555321 is a wasteful number, since it uses less digits than its factorization.

21555321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5871.

The product of its digits is 1500, while the sum is 24.

The square root of 21555321 is about 4642.7708321648. The cubic root of 21555321 is about 278.3031775170.

The spelling of 21555321 in words is "twenty-one million, five hundred fifty-five thousand, three hundred twenty-one".