21858913 has 2 divisors, whose sum is σ = 21858914. Its totient is φ = 21858912.

The previous prime is 21858899. The next prime is 21858929. The reversal of 21858913 is 31985812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21827584 + 31329 = 4672^2 + 177^2 .

It is a cyclic number.

It is not a de Polignac number, because 21858913 - 2¹³ = 21850721 is a prime.

It is a super-3 number, since 3×21858913³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21852913) 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, 10929456 + 10929457.

It is an arithmetic number, because the mean of its divisors is an integer number (10929457).

Almost surely, 2^21858913 is an apocalyptic number.

It is an amenable number.

21858913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21858913 is an equidigital number, since it uses as much as digits as its factorization.

21858913 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 21858913 is about 4675.3516445290. The cubic root of 21858913 is about 279.6036611876.

The spelling of 21858913 in words is "twenty-one million, eight hundred fifty-eight thousand, nine hundred thirteen".