21491912 has 32 divisors (see below), whose sum is σ = 43659000. Its totient is φ = 9859584.

The previous prime is 21491881. The next prime is 21491923. The reversal of 21491912 is 21919412.

It can be written as a sum of positive squares in 4 ways, for example, as 21473956 + 17956 = 4634^2 + 134^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19964 + ... + 21012.

Almost surely, 2^21491912 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21491912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21829500).

21491912 is an abundant number, since it is smaller than the sum of its proper divisors (22167088).

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

21491912 is a wasteful number, since it uses less digits than its factorization.

21491912 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1265 (or 1261 counting only the distinct ones).

The product of its digits is 1296, while the sum is 29.

The square root of 21491912 is about 4635.9370142399. The cubic root of 21491912 is about 278.0300159092.

The spelling of 21491912 in words is "twenty-one million, four hundred ninety-one thousand, nine hundred twelve".