21388271 has 2 divisors, whose sum is σ = 21388272. Its totient is φ = 21388270.

The previous prime is 21388249. The next prime is 21388277. The reversal of 21388271 is 17288312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21388271 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21388277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694135 + 10694136.

It is an arithmetic number, because the mean of its divisors is an integer number (10694136).

Almost surely, 2^21388271 is an apocalyptic number.

21388271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388271 is an equidigital number, since it uses as much as digits as its factorization.

21388271 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5376, while the sum is 32.

The square root of 21388271 is about 4624.7455065117. The cubic root of 21388271 is about 277.5823784862.

The spelling of 21388271 in words is "twenty-one million, three hundred eighty-eight thousand, two hundred seventy-one".