21537423 has 12 divisors (see below), whose sum is σ = 31868928. Its totient is φ = 14007840.

The previous prime is 21537391. The next prime is 21537427. The reversal of 21537423 is 32473512.

It is not a de Polignac number, because 21537423 - 2⁵ = 21537391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21537427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28815 + ... + 29552.

It is an arithmetic number, because the mean of its divisors is an integer number (2655744).

Almost surely, 2^21537423 is an apocalyptic number.

21537423 is a deficient number, since it is larger than the sum of its proper divisors (10331505).

21537423 is a wasteful number, since it uses less digits than its factorization.

21537423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58414 (or 58411 counting only the distinct ones).

The product of its digits is 5040, while the sum is 27.

The square root of 21537423 is about 4640.8429191258. The cubic root of 21537423 is about 278.2261284897.

The spelling of 21537423 in words is "twenty-one million, five hundred thirty-seven thousand, four hundred twenty-three".