21540510 has 48 divisors (see below), whose sum is σ = 56446416. Its totient is φ = 5698944.

The previous prime is 21540473. The next prime is 21540529. The reversal of 21540510 is 1504512.

21540510 is a `hidden beast` number, since 2 + 154 + 0 + 510 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11457 + ... + 13203.

It is an arithmetic number, because the mean of its divisors is an integer number (1175967).

Almost surely, 2^21540510 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21540510, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28223208).

21540510 is an abundant number, since it is smaller than the sum of its proper divisors (34905906).

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

21540510 is a wasteful number, since it uses less digits than its factorization.

21540510 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1897 (or 1894 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21540510 is about 4641.1754976514. The cubic root of 21540510 is about 278.2394207489.

The spelling of 21540510 in words is "twenty-one million, five hundred forty thousand, five hundred ten".