20643231 has 16 divisors (see below), whose sum is σ = 31635968. Its totient is φ = 11728800.

The previous prime is 20643229. The next prime is 20643239. The reversal of 20643231 is 13234602.

It is a happy number.

It is not a de Polignac number, because 20643231 - 2¹ = 20643229 is a prime.

It is a super-2 number, since 2×20643231² = 852285972238722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 20643198 and 20643207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20643239) 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, 1086 + ... + 6516.

It is an arithmetic number, because the mean of its divisors is an integer number (1977248).

Almost surely, 2^20643231 is an apocalyptic number.

20643231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

20643231 is a deficient number, since it is larger than the sum of its proper divisors (10992737).

20643231 is a wasteful number, since it uses less digits than its factorization.

20643231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5622.

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 20643231 is about 4543.4822548349. The cubic root of 20643231 is about 274.3211066603.

Adding to 20643231 its reverse (13234602), we get a palindrome (33877833).

The spelling of 20643231 in words is "twenty million, six hundred forty-three thousand, two hundred thirty-one".