21858931 has 2 divisors, whose sum is σ = 21858932. Its totient is φ = 21858930.

The previous prime is 21858929. The next prime is 21858979. The reversal of 21858931 is 13985812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21858931 - 2¹ = 21858929 is a prime.

It is a super-3 number, since 3×21858931³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 21858929, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21858731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10929465 + 10929466.

It is an arithmetic number, because the mean of its divisors is an integer number (10929466).

Almost surely, 2^21858931 is an apocalyptic number.

21858931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21858931 is an equidigital number, since it uses as much as digits as its factorization.

21858931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 37.

The square root of 21858931 is about 4675.3535695175. The cubic root of 21858931 is about 279.6037379353.

The spelling of 21858931 in words is "twenty-one million, eight hundred fifty-eight thousand, nine hundred thirty-one".