21531393 has 16 divisors (see below), whose sum is σ = 34352640. Its totient is φ = 13249872.

The previous prime is 21531379. The next prime is 21531439. The reversal of 21531393 is 39313512.

It is a happy number.

It is not a de Polignac number, because 21531393 - 2⁵ = 21531361 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21531343) 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, 30321 + ... + 31022.

It is an arithmetic number, because the mean of its divisors is an integer number (2147040).

Almost surely, 2^21531393 is an apocalyptic number.

It is an amenable number.

21531393 is a deficient number, since it is larger than the sum of its proper divisors (12821247).

21531393 is a wasteful number, since it uses less digits than its factorization.

21531393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61365 (or 61359 counting only the distinct ones).

The product of its digits is 2430, while the sum is 27.

The square root of 21531393 is about 4640.1932071844. The cubic root of 21531393 is about 278.2001603543.

The spelling of 21531393 in words is "twenty-one million, five hundred thirty-one thousand, three hundred ninety-three".