21163481 has 2 divisors, whose sum is σ = 21163482. Its totient is φ = 21163480.

The previous prime is 21163469. The next prime is 21163507. The reversal of 21163481 is 18436112.

It is an a-pointer prime, because the next prime (21163507) can be obtained adding 21163481 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21160000 + 3481 = 4600^2 + 59^2 .

It is a cyclic number.

It is not a de Polignac number, because 21163481 - 2²² = 16969177 is a prime.

It is a super-2 number, since 2×21163481² = 895785856074722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21163481.

It is not a weakly prime, because it can be changed into another prime (21163411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10581740 + 10581741.

It is an arithmetic number, because the mean of its divisors is an integer number (10581741).

Almost surely, 2^21163481 is an apocalyptic number.

It is an amenable number.

21163481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21163481 is an equidigital number, since it uses as much as digits as its factorization.

21163481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 26.

The square root of 21163481 is about 4600.3783540052. The cubic root of 21163481 is about 276.6064911626.

Adding to 21163481 its reverse (18436112), we get a palindrome (39599593).

It can be divided in two parts, 2116 and 3481, that multiplied together give a square (7365796 = 2714²).

The spelling of 21163481 in words is "twenty-one million, one hundred sixty-three thousand, four hundred eighty-one".