21591423 has 24 divisors (see below), whose sum is σ = 35987328. Its totient is φ = 12218832.

The previous prime is 21591421. The next prime is 21591433. The reversal of 21591423 is 32419512.

It is not a de Polignac number, because 21591423 - 2¹ = 21591421 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21591421) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5140 + ... + 8342.

It is an arithmetic number, because the mean of its divisors is an integer number (1499472).

Almost surely, 2^21591423 is an apocalyptic number.

21591423 is a deficient number, since it is larger than the sum of its proper divisors (14395905).

21591423 is a wasteful number, since it uses less digits than its factorization.

21591423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3323 (or 3320 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 21591423 is about 4646.6571855475. The cubic root of 21591423 is about 278.4584631853.

The spelling of 21591423 in words is "twenty-one million, five hundred ninety-one thousand, four hundred twenty-three".