21491610 has 64 divisors (see below), whose sum is σ = 60998400. Its totient is φ = 4741632.

The previous prime is 21491579. The next prime is 21491627. The reversal of 21491610 is 1619412.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4326 + ... + 7854.

It is an arithmetic number, because the mean of its divisors is an integer number (953100).

Almost surely, 2^21491610 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21491610, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30499200).

21491610 is an abundant number, since it is smaller than the sum of its proper divisors (39506790).

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

21491610 is a wasteful number, since it uses less digits than its factorization.

21491610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3575.

The product of its (nonzero) digits is 432, while the sum is 24.

The square root of 21491610 is about 4635.9044425009. The cubic root of 21491610 is about 278.0287136292.

The spelling of 21491610 in words is "twenty-one million, four hundred ninety-one thousand, six hundred ten".