20643381 has 12 divisors (see below), whose sum is σ = 32529120. Its totient is φ = 12511080.

The previous prime is 20643379. The next prime is 20643407. The reversal of 20643381 is 18334602.

It is a happy number.

It is not a de Polignac number, because 20643381 - 2¹ = 20643379 is a prime.

It is a super-2 number, since 2×20643381² = 852298358222322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20693381) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 104161 + ... + 104358.

It is an arithmetic number, because the mean of its divisors is an integer number (2710760).

Almost surely, 2^20643381 is an apocalyptic number.

It is an amenable number.

20643381 is a deficient number, since it is larger than the sum of its proper divisors (11885739).

20643381 is a wasteful number, since it uses less digits than its factorization.

20643381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208536 (or 208533 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 20643381 is about 4543.4987619675. The cubic root of 20643381 is about 274.3217710923.

Adding to 20643381 its reverse (18334602), we get a palindrome (38977983).

It can be divided in two parts, 2064 and 3381, that added together give a palindrome (5445).

The spelling of 20643381 in words is "twenty million, six hundred forty-three thousand, three hundred eighty-one".