21047540 has 24 divisors (see below), whose sum is σ = 45142272. Its totient is φ = 8239520.

The previous prime is 21047539. The next prime is 21047563. The reversal of 21047540 is 4574012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10256 + ... + 12135.

It is an arithmetic number, because the mean of its divisors is an integer number (1880928).

Almost surely, 2^21047540 is an apocalyptic number.

21047540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21047540 is an abundant number, since it is smaller than the sum of its proper divisors (24094732).

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

21047540 is a wasteful number, since it uses less digits than its factorization.

21047540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22447 (or 22445 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21047540 is about 4587.7598019077. The cubic root of 21047540 is about 276.1004500293.

The spelling of 21047540 in words is "twenty-one million, forty-seven thousand, five hundred forty".