21543831 has 6 divisors (see below), whose sum is σ = 31118880. Its totient is φ = 14362548.

The previous prime is 21543829. The next prime is 21543859. The reversal of 21543831 is 13834512.

It is a happy number.

It is not a de Polignac number, because 21543831 - 2¹ = 21543829 is a prime.

It is a super-2 number, since 2×21543831² = 928273308313122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21543795 and 21543804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543881) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196871 + ... + 1196888.

It is an arithmetic number, because the mean of its divisors is an integer number (5186480).

Almost surely, 2^21543831 is an apocalyptic number.

21543831 is a deficient number, since it is larger than the sum of its proper divisors (9575049).

21543831 is a wasteful number, since it uses less digits than its factorization.

21543831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2393765 (or 2393762 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21543831 is about 4641.5332596029. The cubic root of 21543831 is about 278.2537191667.

The spelling of 21543831 in words is "twenty-one million, five hundred forty-three thousand, eight hundred thirty-one".