21544537 has 16 divisors (see below), whose sum is σ = 27048960. Its totient is φ = 16731792.

The previous prime is 21544531. The next prime is 21544541. The reversal of 21544537 is 73544512.

It is not a de Polignac number, because 21544537 - 2⁷ = 21544409 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21544499 and 21544508.

It is not an unprimeable number, because it can be changed into a prime (21544531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 463 + ... + 6580.

It is an arithmetic number, because the mean of its divisors is an integer number (1690560).

Almost surely, 2^21544537 is an apocalyptic number.

It is an amenable number.

21544537 is a deficient number, since it is larger than the sum of its proper divisors (5504423).

21544537 is a wasteful number, since it uses less digits than its factorization.

21544537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7092.

The product of its digits is 16800, while the sum is 31.

The square root of 21544537 is about 4641.6093114350. The cubic root of 21544537 is about 278.2567586289.

The spelling of 21544537 in words is "twenty-one million, five hundred forty-four thousand, five hundred thirty-seven".