20661665 has 8 divisors (see below), whose sum is σ = 24848640. Its totient is φ = 16492912.

The previous prime is 20661643. The next prime is 20661689. The reversal of 20661665 is 56616602.

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 20661665 - 2¹² = 20657569 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1919 + ... + 6708.

It is an arithmetic number, because the mean of its divisors is an integer number (3106080).

Almost surely, 2^20661665 is an apocalyptic number.

It is an amenable number.

20661665 is a deficient number, since it is larger than the sum of its proper divisors (4186975).

20661665 is an equidigital number, since it uses as much as digits as its factorization.

20661665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9111.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 20661665 is about 4545.5104223838. The cubic root of 20661665 is about 274.4027368213.

The spelling of 20661665 in words is "twenty million, six hundred sixty-one thousand, six hundred sixty-five".