21491208 has 48 divisors (see below), whose sum is σ = 58425900. Its totient is φ = 7136640.

The previous prime is 21491201. The next prime is 21491209. The reversal of 21491208 is 80219412.

It can be written as a sum of positive squares in 2 ways, for example, as 15350724 + 6140484 = 3918^2 + 2478^2 .

It is not an unprimeable number, because it can be changed into a prime (21491201) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29958 + ... + 30666.

Almost surely, 2^21491208 is an apocalyptic number.

It is an amenable number.

21491208 is an abundant number, since it is smaller than the sum of its proper divisors (36934692).

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

21491208 is a wasteful number, since it uses less digits than its factorization.

21491208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1142 (or 1135 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 21491208 is about 4635.8610850628. The cubic root of 21491208 is about 278.0269801118.

The spelling of 21491208 in words is "twenty-one million, four hundred ninety-one thousand, two hundred eight".