21438187 has 2 divisors, whose sum is σ = 21438188. Its totient is φ = 21438186.

The previous prime is 21438103. The next prime is 21438211. The reversal of 21438187 is 78183412.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21438187 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21438787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719093 + 10719094.

It is an arithmetic number, because the mean of its divisors is an integer number (10719094).

Almost surely, 2^21438187 is an apocalyptic number.

21438187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21438187 is an equidigital number, since it uses as much as digits as its factorization.

21438187 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10752, while the sum is 34.

The square root of 21438187 is about 4630.1389827952. The cubic root of 21438187 is about 277.7981515308.

The spelling of 21438187 in words is "twenty-one million, four hundred thirty-eight thousand, one hundred eighty-seven".