20181664 has 12 divisors (see below), whose sum is σ = 39732714. Its totient is φ = 10090816.

The previous prime is 20181643. The next prime is 20181671. The reversal of 20181664 is 46618102.

It can be written as a sum of positive squares in only one way, i.e., 20178064 + 3600 = 4492^2 + 60^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 315307 + ... + 315370.

Almost surely, 2^20181664 is an apocalyptic number.

It is an amenable number.

20181664 is a deficient number, since it is larger than the sum of its proper divisors (19551050).

20181664 is an equidigital number, since it uses as much as digits as its factorization.

20181664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 630687 (or 630679 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 20181664 is about 4492.4006945062. The cubic root of 20181664 is about 272.2611390580.

Adding to 20181664 its reverse (46618102), we get a palindrome (66799766).

The spelling of 20181664 in words is "twenty million, one hundred eighty-one thousand, six hundred sixty-four".