21543151 has 4 divisors (see below), whose sum is σ = 24620752. Its totient is φ = 18465552.

The previous prime is 21543133. The next prime is 21543173. The reversal of 21543151 is 15134512.

It is a happy number.

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

It is not a de Polignac number, because 21543151 - 2⁹ = 21542639 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1538790 + ... + 1538803.

It is an arithmetic number, because the mean of its divisors is an integer number (6155188).

Almost surely, 2^21543151 is an apocalyptic number.

21543151 is a deficient number, since it is larger than the sum of its proper divisors (3077601).

21543151 is an equidigital number, since it uses as much as digits as its factorization.

21543151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3077600.

The product of its digits is 600, while the sum is 22.

The square root of 21543151 is about 4641.4600073684. The cubic root of 21543151 is about 278.2507915766.

Adding to 21543151 its reverse (15134512), we get a palindrome (36677663).

The spelling of 21543151 in words is "twenty-one million, five hundred forty-three thousand, one hundred fifty-one".