21654547 has 4 divisors (see below), whose sum is σ = 22794280. Its totient is φ = 20514816.

The previous prime is 21654541. The next prime is 21654559. The reversal of 21654547 is 74545612.

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

It is a cyclic number.

It is not a de Polignac number, because 21654547 - 2⁷ = 21654419 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21654541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 569838 + ... + 569875.

It is an arithmetic number, because the mean of its divisors is an integer number (5698570).

Almost surely, 2^21654547 is an apocalyptic number.

21654547 is a deficient number, since it is larger than the sum of its proper divisors (1139733).

21654547 is a wasteful number, since it uses less digits than its factorization.

21654547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1139732.

The product of its digits is 33600, while the sum is 34.

The square root of 21654547 is about 4653.4446381149. Note that the first 3 decimals coincide. The cubic root of 21654547 is about 278.7295632761.

It can be divided in two parts, 21654 and 547, that added together give a square (22201 = 149²).

The spelling of 21654547 in words is "twenty-one million, six hundred fifty-four thousand, five hundred forty-seven".