21706830 has 96 divisors (see below), whose sum is σ = 59304960. Its totient is φ = 5503680.

The previous prime is 21706823. The next prime is 21706837. The reversal of 21706830 is 3860712.

It is an interprime number because it is at equal distance from previous prime (21706823) and next prime (21706837).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21706794 and 21706803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21706837) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 274731 + ... + 274809.

It is an arithmetic number, because the mean of its divisors is an integer number (617760).

Almost surely, 2^21706830 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21706830, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29652480).

21706830 is an abundant number, since it is smaller than the sum of its proper divisors (37598130).

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

21706830 is a wasteful number, since it uses less digits than its factorization.

21706830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 203 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21706830 is about 4659.0589178503. The cubic root of 21706830 is about 278.9537056576.

The spelling of 21706830 in words is "twenty-one million, seven hundred six thousand, eight hundred thirty".