21055545 has 60 divisors (see below), whose sum is σ = 43947684. Its totient is φ = 9616320.

The previous prime is 21055543. The next prime is 21055561. The reversal of 21055545 is 54555012.

21055545 is a `hidden beast` number, since 2 + 105 + 554 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10732176 + 10323369 = 3276^2 + 3213^2 .

It is not a de Polignac number, because 21055545 - 2¹ = 21055543 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21055543) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 19315 + ... + 20375.

Almost surely, 2^21055545 is an apocalyptic number.

It is an amenable number.

21055545 is an abundant number, since it is smaller than the sum of its proper divisors (22892139).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21055545 is a wasteful number, since it uses less digits than its factorization.

21055545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1092 (or 1076 counting only the distinct ones).

The product of its (nonzero) digits is 5000, while the sum is 27.

The square root of 21055545 is about 4588.6321491268. The cubic root of 21055545 is about 276.1354486398.

It can be divided in two parts, 210 and 55545, that added together give a palindrome (55755).

The spelling of 21055545 in words is "twenty-one million, fifty-five thousand, five hundred forty-five".