21071908 has 72 divisors (see below), whose sum is σ = 46453176. Its totient is φ = 8279040.

The previous prime is 21071903. The next prime is 21071917. The reversal of 21071908 is 80917012.

It can be written as a sum of positive squares in 4 ways, for example, as 8054244 + 13017664 = 2838^2 + 3608^2 .

It is not an unprimeable number, because it can be changed into a prime (21071903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 106866 + ... + 107062.

It is an arithmetic number, because the mean of its divisors is an integer number (645183).

Almost surely, 2^21071908 is an apocalyptic number.

It is an amenable number.

21071908 is an abundant number, since it is smaller than the sum of its proper divisors (25381268).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21071908 is a wasteful number, since it uses less digits than its factorization.

21071908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 253 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21071908 is about 4590.4147960724. The cubic root of 21071908 is about 276.2069616210.

The spelling of 21071908 in words is "twenty-one million, seventy-one thousand, nine hundred eight".