21143531 has 8 divisors (see below), whose sum is σ = 21525504. Its totient is φ = 20765160.

The previous prime is 21143497. The next prime is 21143533. The reversal of 21143531 is 13534112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21143531 - 2²² = 16949227 is a prime.

It is a super-2 number, since 2×21143531² = 894097806295922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21143533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12710 + ... + 14276.

It is an arithmetic number, because the mean of its divisors is an integer number (2690688).

Almost surely, 2^21143531 is an apocalyptic number.

21143531 is a deficient number, since it is larger than the sum of its proper divisors (381973).

21143531 is a wasteful number, since it uses less digits than its factorization.

21143531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1801.

The product of its digits is 360, while the sum is 20.

The square root of 21143531 is about 4598.2095428547. The cubic root of 21143531 is about 276.5195484022.

Adding to 21143531 its reverse (13534112), we get a palindrome (34677643).

The spelling of 21143531 in words is "twenty-one million, one hundred forty-three thousand, five hundred thirty-one".