21540549 has 16 divisors (see below), whose sum is σ = 30189632. Its totient is φ = 13644288.

The previous prime is 21540529. The next prime is 21540551. The reversal of 21540549 is 94504512.

It is not a de Polignac number, because 21540549 - 2¹² = 21536453 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540529) 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, 2517 + ... + 7029.

It is an arithmetic number, because the mean of its divisors is an integer number (1886852).

Almost surely, 2^21540549 is an apocalyptic number.

It is an amenable number.

21540549 is a deficient number, since it is larger than the sum of its proper divisors (8649083).

21540549 is a wasteful number, since it uses less digits than its factorization.

21540549 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4596.

The product of its (nonzero) digits is 7200, while the sum is 30.

The square root of 21540549 is about 4641.1796991713. The cubic root of 21540549 is about 278.2395886702.

The spelling of 21540549 in words is "twenty-one million, five hundred forty thousand, five hundred forty-nine".