21263993 has 2 divisors, whose sum is σ = 21263994. Its totient is φ = 21263992.

The previous prime is 21263987. The next prime is 21264017. The reversal of 21263993 is 39936212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11202409 + 10061584 = 3347^2 + 3172^2 .

It is a cyclic number.

It is not a de Polignac number, because 21263993 - 2¹² = 21259897 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21263903) 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, 10631996 + 10631997.

It is an arithmetic number, because the mean of its divisors is an integer number (10631997).

Almost surely, 2^21263993 is an apocalyptic number.

It is an amenable number.

21263993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21263993 is an equidigital number, since it uses as much as digits as its factorization.

21263993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 35.

The square root of 21263993 is about 4611.2897328188. The cubic root of 21263993 is about 277.0436967040.

The spelling of 21263993 in words is "twenty-one million, two hundred sixty-three thousand, nine hundred ninety-three".