21170881 has 2 divisors, whose sum is σ = 21170882. Its totient is φ = 21170880.

The previous prime is 21170857. The next prime is 21170887. The reversal of 21170881 is 18807112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 194481 = 4580^2 + 441^2 .

It is a cyclic number.

It is not a de Polignac number, because 21170881 - 2⁷ = 21170753 is a prime.

It is a super-2 number, since 2×21170881² = 896412404632322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21170887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585440 + 10585441.

It is an arithmetic number, because the mean of its divisors is an integer number (10585441).

Almost surely, 2^21170881 is an apocalyptic number.

It is an amenable number.

21170881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21170881 is an equidigital number, since it uses as much as digits as its factorization.

21170881 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 21170881 is about 4601.1825653847. The cubic root of 21170881 is about 276.6387267151.

Adding to 21170881 its reverse (18807112), we get a palindrome (39977993).

The spelling of 21170881 in words is "twenty-one million, one hundred seventy thousand, eight hundred eighty-one".