21612545 has 4 divisors (see below), whose sum is σ = 25935060. Its totient is φ = 17290032.

The previous prime is 21612529. The next prime is 21612581. The reversal of 21612545 is 54521612.

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 5193841 + 16418704 = 2279^2 + 4052^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612545 - 2⁴ = 21612529 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2161250 + ... + 2161259.

It is an arithmetic number, because the mean of its divisors is an integer number (6483765).

Almost surely, 2^21612545 is an apocalyptic number.

It is an amenable number.

21612545 is a deficient number, since it is larger than the sum of its proper divisors (4322515).

21612545 is an equidigital number, since it uses as much as digits as its factorization.

21612545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4322514.

The product of its digits is 2400, while the sum is 26.

The square root of 21612545 is about 4648.9294466576. The cubic root of 21612545 is about 278.5492350748.

The spelling of 21612545 in words is "twenty-one million, six hundred twelve thousand, five hundred forty-five".