21555423 has 16 divisors (see below), whose sum is σ = 32798560. Its totient is φ = 13981248.

The previous prime is 21555407. The next prime is 21555433. The reversal of 21555423 is 32455512.

It is a happy number.

It is not a de Polignac number, because 21555423 - 2⁴ = 21555407 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555433) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9790 + ... + 11787.

It is an arithmetic number, because the mean of its divisors is an integer number (2049910).

Almost surely, 2^21555423 is an apocalyptic number.

21555423 is a deficient number, since it is larger than the sum of its proper divisors (11243137).

21555423 is a wasteful number, since it uses less digits than its factorization.

21555423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21623 (or 21617 counting only the distinct ones).

The product of its digits is 6000, while the sum is 27.

The square root of 21555423 is about 4642.7818169714. The cubic root of 21555423 is about 278.3036164942.

The spelling of 21555423 in words is "twenty-one million, five hundred fifty-five thousand, four hundred twenty-three".