20861661 has 8 divisors (see below), whose sum is σ = 28494144. Its totient is φ = 13568480.

The previous prime is 20861653. The next prime is 20861663. The reversal of 20861661 is 16616802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20861661 - 2³ = 20861653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20861663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 84681 + ... + 84926.

It is an arithmetic number, because the mean of its divisors is an integer number (3561768).

Almost surely, 2^20861661 is an apocalyptic number.

It is an amenable number.

20861661 is a deficient number, since it is larger than the sum of its proper divisors (7632483).

20861661 is a wasteful number, since it uses less digits than its factorization.

20861661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169651.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 20861661 is about 4567.4567321432. The cubic root of 20861661 is about 275.2852621172.

The spelling of 20861661 in words is "twenty million, eight hundred sixty-one thousand, six hundred sixty-one".