21981763 has 2 divisors, whose sum is σ = 21981764. Its totient is φ = 21981762.

The previous prime is 21981749. The next prime is 21981793. The reversal of 21981763 is 36718912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21981763 - 2⁹ = 21981251 is a prime.

It is equal to p_1388179 and since 21981763 and 1388179 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21981733) 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, 10990881 + 10990882.

It is an arithmetic number, because the mean of its divisors is an integer number (10990882).

Almost surely, 2^21981763 is an apocalyptic number.

21981763 is a deficient number, since it is larger than the sum of its proper divisors (1).

21981763 is an equidigital number, since it uses as much as digits as its factorization.

21981763 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 37.

The square root of 21981763 is about 4688.4712860377. The cubic root of 21981763 is about 280.1264862203.

The spelling of 21981763 in words is "twenty-one million, nine hundred eighty-one thousand, seven hundred sixty-three".