21808753 has 2 divisors, whose sum is σ = 21808754. Its totient is φ = 21808752.

The previous prime is 21808729. The next prime is 21808757. The reversal of 21808753 is 35780812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21687649 + 121104 = 4657^2 + 348^2 .

It is a cyclic number.

It is not a de Polignac number, because 21808753 - 2¹⁷ = 21677681 is a prime.

It is not a weakly prime, because it can be changed into another prime (21808757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10904376 + 10904377.

It is an arithmetic number, because the mean of its divisors is an integer number (10904377).

Almost surely, 2^21808753 is an apocalyptic number.

It is an amenable number.

21808753 is a deficient number, since it is larger than the sum of its proper divisors (1).

21808753 is an equidigital number, since it uses as much as digits as its factorization.

21808753 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 21808753 is about 4669.9842612154. The cubic root of 21808753 is about 279.3896270454.

The spelling of 21808753 in words is "twenty-one million, eight hundred eight thousand, seven hundred fifty-three".