21054561 has 16 divisors (see below), whose sum is σ = 30932928. Its totient is φ = 12632000.

The previous prime is 21054559. The next prime is 21054569. The reversal of 21054561 is 16545012.

It is a cyclic number.

It is not a de Polignac number, because 21054561 - 2¹ = 21054559 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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

It is not an unprimeable number, because it can be changed into a prime (21054569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 175 + ... + 6491.

It is an arithmetic number, because the mean of its divisors is an integer number (1933308).

Almost surely, 2^21054561 is an apocalyptic number.

It is an amenable number.

21054561 is a deficient number, since it is larger than the sum of its proper divisors (9878367).

21054561 is a wasteful number, since it uses less digits than its factorization.

21054561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6432.

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 21054561 is about 4588.5249263788. The cubic root of 21054561 is about 276.1311469778.

Adding to 21054561 its reverse (16545012), we get a palindrome (37599573).

It can be divided in two parts, 2105 and 4561, that added together give a palindrome (6666).

The spelling of 21054561 in words is "twenty-one million, fifty-four thousand, five hundred sixty-one".