21665070 has 80 divisors (see below), whose sum is σ = 66594528. Its totient is φ = 4950720.

The previous prime is 21665041. The next prime is 21665071. The reversal of 21665070 is 7056612.

21665070 is a `hidden beast` number, since 2 + 1 + 6 + 650 + 7 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665071) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 3760 + ... + 7580.

Almost surely, 2^21665070 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21665070, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33297264).

21665070 is an abundant number, since it is smaller than the sum of its proper divisors (44929458).

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

21665070 is a wasteful number, since it uses less digits than its factorization.

21665070 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3847 (or 3838 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 21665070 is about 4654.5751685841. The cubic root of 21665070 is about 278.7747053921.

The spelling of 21665070 in words is "twenty-one million, six hundred sixty-five thousand, seventy".