21545541 has 16 divisors (see below), whose sum is σ = 32699520. Its totient is φ = 14012640.

The previous prime is 21545509. The next prime is 21545551. The reversal of 21545541 is 14554512.

It is not a de Polignac number, because 21545541 - 2⁵ = 21545509 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545501) 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, 8625 + ... + 10838.

It is an arithmetic number, because the mean of its divisors is an integer number (2043720).

Almost surely, 2^21545541 is an apocalyptic number.

It is an amenable number.

21545541 is a deficient number, since it is larger than the sum of its proper divisors (11153979).

21545541 is a wasteful number, since it uses less digits than its factorization.

21545541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19513 (or 19507 counting only the distinct ones).

The product of its digits is 4000, while the sum is 27.

The square root of 21545541 is about 4641.7174623193. The cubic root of 21545541 is about 278.2610809225.

It can be divided in two parts, 215455 and 41, that added together give a triangular number (215496 = T₆₅₆).

The spelling of 21545541 in words is "twenty-one million, five hundred forty-five thousand, five hundred forty-one".