21537871 has 2 divisors, whose sum is σ = 21537872. Its totient is φ = 21537870.

The previous prime is 21537869. The next prime is 21537881. The reversal of 21537871 is 17873512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21537871 - 2¹ = 21537869 is a prime.

Together with 21537869, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21537851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768935 + 10768936.

It is an arithmetic number, because the mean of its divisors is an integer number (10768936).

Almost surely, 2^21537871 is an apocalyptic number.

21537871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21537871 is an equidigital number, since it uses as much as digits as its factorization.

21537871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11760, while the sum is 34.

The square root of 21537871 is about 4640.8911859685. The cubic root of 21537871 is about 278.2280576039.

The spelling of 21537871 in words is "twenty-one million, five hundred thirty-seven thousand, eight hundred seventy-one".