20961666 has 56 divisors (see below), whose sum is σ = 51467184. Its totient is φ = 6347160.

The previous prime is 20961649. The next prime is 20961667. The reversal of 20961666 is 66616902.

It is a happy number.

It is a super-4 number, since 4×20961666⁴ (a number of 30 digits) contains 4444 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20961666.

It is not an unprimeable number, because it can be changed into a prime (20961667) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 15385 + ... + 16691.

Almost surely, 2^20961666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20961666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25733592).

20961666 is an abundant number, since it is smaller than the sum of its proper divisors (30505518).

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

20961666 is a wasteful number, since it uses less digits than its factorization.

20961666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1338 (or 1323 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 20961666 is about 4578.3912021582. The cubic root of 20961666 is about 275.7244414198.

The spelling of 20961666 in words is "twenty million, nine hundred sixty-one thousand, six hundred sixty-six".