21161331 has 10 divisors (see below), whose sum is σ = 31611492. Its totient is φ = 14107500.

The previous prime is 21161323. The next prime is 21161377. The reversal of 21161331 is 13316112.

21161331 is a `hidden beast` number, since 21 + 1 + 613 + 31 = 666.

It is not a de Polignac number, because 21161331 - 2³ = 21161323 is a prime.

It is a super-2 number, since 2×21161331² = 895603859383122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21161321) 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 in 9 ways as a sum of consecutive naturals, for example, 130545 + ... + 130706.

Almost surely, 2^21161331 is an apocalyptic number.

21161331 is a deficient number, since it is larger than the sum of its proper divisors (10450161).

21161331 is an equidigital number, since it uses as much as digits as its factorization.

21161331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261263 (or 261254 counting only the distinct ones).

The product of its digits is 108, while the sum is 18.

The square root of 21161331 is about 4600.1446716381. The cubic root of 21161331 is about 276.5971240190.

Adding to 21161331 its reverse (13316112), we get a palindrome (34477443).

The spelling of 21161331 in words is "twenty-one million, one hundred sixty-one thousand, three hundred thirty-one".