20623681 has 4 divisors (see below), whose sum is σ = 22210132. Its totient is φ = 19037232.

The previous prime is 20623643. The next prime is 20623693. The reversal of 20623681 is 18632602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7728400 + 12895281 = 2780^2 + 3591^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20623681 is a prime.

It is a super-2 number, since 2×20623681² = 850672435979522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20623621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 793206 + ... + 793231.

It is an arithmetic number, because the mean of its divisors is an integer number (5552533).

Almost surely, 2^20623681 is an apocalyptic number.

It is an amenable number.

20623681 is a deficient number, since it is larger than the sum of its proper divisors (1586451).

20623681 is a wasteful number, since it uses less digits than its factorization.

20623681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1586450.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 20623681 is about 4541.3303117038. The cubic root of 20623681 is about 274.2344814689.

The spelling of 20623681 in words is "twenty million, six hundred twenty-three thousand, six hundred eighty-one".