20172661 has 16 divisors (see below), whose sum is σ = 22694400. Its totient is φ = 17841600.

The previous prime is 20172643. The next prime is 20172667. The reversal of 20172661 is 16627102.

It is a cyclic number.

It is not a de Polignac number, because 20172661 - 2¹⁵ = 20139893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20172667) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16491 + ... + 17671.

It is an arithmetic number, because the mean of its divisors is an integer number (1418400).

Almost surely, 2^20172661 is an apocalyptic number.

It is an amenable number.

20172661 is a deficient number, since it is larger than the sum of its proper divisors (2521739).

20172661 is a wasteful number, since it uses less digits than its factorization.

20172661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 20172661 is about 4491.3985572425. The cubic root of 20172661 is about 272.2206479863.

Adding to 20172661 its reverse (16627102), we get a palindrome (36799763).

The spelling of 20172661 in words is "twenty million, one hundred seventy-two thousand, six hundred sixty-one".