21187493 has 8 divisors (see below), whose sum is σ = 21530208. Its totient is φ = 20847024.

The previous prime is 21187469. The next prime is 21187511. The reversal of 21187493 is 39478112.

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

It is a cyclic number.

It is not a de Polignac number, because 21187493 - 2¹⁰ = 21186469 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21187193) 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, 32630 + ... + 33272.

It is an arithmetic number, because the mean of its divisors is an integer number (2691276).

Almost surely, 2^21187493 is an apocalyptic number.

It is an amenable number.

21187493 is a deficient number, since it is larger than the sum of its proper divisors (342715).

21187493 is an equidigital number, since it uses as much as digits as its factorization.

21187493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1123.

The product of its digits is 12096, while the sum is 35.

The square root of 21187493 is about 4602.9873995048. The cubic root of 21187493 is about 276.7110638256.

The spelling of 21187493 in words is "twenty-one million, one hundred eighty-seven thousand, four hundred ninety-three".