21500545 has 16 divisors (see below), whose sum is σ = 28288512. Its totient is φ = 15557760.

The previous prime is 21500543. The next prime is 21500587. The reversal of 21500545 is 54500512.

It is not a de Polignac number, because 21500545 - 2¹ = 21500543 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21500543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11389 + ... + 13141.

It is an arithmetic number, because the mean of its divisors is an integer number (1768032).

Almost surely, 2^21500545 is an apocalyptic number.

It is an amenable number.

21500545 is a deficient number, since it is larger than the sum of its proper divisors (6787967).

21500545 is a wasteful number, since it uses less digits than its factorization.

21500545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1992.

The product of its (nonzero) digits is 1000, while the sum is 22.

The square root of 21500545 is about 4636.8680162368. The cubic root of 21500545 is about 278.0672378467.

The spelling of 21500545 in words is "twenty-one million, five hundred thousand, five hundred forty-five".