72543521 has 4 divisors (see below), whose sum is σ = 72711492. Its totient is φ = 72375552.

The previous prime is 72543511. The next prime is 72543563. The reversal of 72543521 is 12534527.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 45711121 + 26832400 = 6761^2 + 5180^2 .

It is a cyclic number.

It is not a de Polignac number, because 72543521 - 2¹⁴ = 72527137 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (72543511) 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, 83336 + ... + 84201.

It is an arithmetic number, because the mean of its divisors is an integer number (18177873).

Almost surely, 2^72543521 is an apocalyptic number.

It is an amenable number.

72543521 is a deficient number, since it is larger than the sum of its proper divisors (167971).

72543521 is a wasteful number, since it uses less digits than its factorization.

72543521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167970.

The product of its digits is 8400, while the sum is 29.

The square root of 72543521 is about 8517.2484406644. The cubic root of 72543521 is about 417.0609648495.

The spelling of 72543521 in words is "seventy-two million, five hundred forty-three thousand, five hundred twenty-one".