21791910 has 64 divisors (see below), whose sum is σ = 61254144. Its totient is φ = 4857600.

The previous prime is 21791897. The next prime is 21791911. The reversal of 21791910 is 1919712.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21791911) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7345 + ... + 9875.

It is an arithmetic number, because the mean of its divisors is an integer number (957096).

Almost surely, 2^21791910 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21791910, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30627072).

21791910 is an abundant number, since it is smaller than the sum of its proper divisors (39462234).

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

21791910 is a wasteful number, since it uses less digits than its factorization.

21791910 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2589.

The product of its (nonzero) digits is 1134, while the sum is 30.

The square root of 21791910 is about 4668.1805877665. The cubic root of 21791910 is about 279.3176838913.

The spelling of 21791910 in words is "twenty-one million, seven hundred ninety-one thousand, nine hundred ten".