21438931 has 2 divisors, whose sum is σ = 21438932. Its totient is φ = 21438930.

The previous prime is 21438913. The next prime is 21438953. The reversal of 21438931 is 13983412.

Together with previous prime (21438913) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21438931 - 2⁹ = 21438419 is a prime.

It is a super-2 number, since 2×21438931² = 919255524845522, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21438893 and 21438902.

It is not a weakly prime, because it can be changed into another prime (21438961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719465 + 10719466.

It is an arithmetic number, because the mean of its divisors is an integer number (10719466).

Almost surely, 2^21438931 is an apocalyptic number.

21438931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21438931 is an equidigital number, since it uses as much as digits as its factorization.

21438931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 31.

The square root of 21438931 is about 4630.2193252588. The cubic root of 21438931 is about 277.8013651022.

The spelling of 21438931 in words is "twenty-one million, four hundred thirty-eight thousand, nine hundred thirty-one".