21865993 has 2 divisors, whose sum is σ = 21865994. Its totient is φ = 21865992.

The previous prime is 21865981. The next prime is 21866003. The reversal of 21865993 is 39956812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20548089 + 1317904 = 4533^2 + 1148^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21865993 is a prime.

It is not a weakly prime, because it can be changed into another prime (21863993) 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, 10932996 + 10932997.

It is an arithmetic number, because the mean of its divisors is an integer number (10932997).

Almost surely, 2^21865993 is an apocalyptic number.

It is an amenable number.

21865993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865993 is an equidigital number, since it uses as much as digits as its factorization.

21865993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 43.

The square root of 21865993 is about 4676.1087455276. The cubic root of 21865993 is about 279.6338453697.

The spelling of 21865993 in words is "twenty-one million, eight hundred sixty-five thousand, nine hundred ninety-three".