21078540 has 72 divisors (see below), whose sum is σ = 73076640. Its totient is φ = 4817664.

The previous prime is 21078527. The next prime is 21078559. The reversal of 21078540 is 4587012.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7105 + ... + 9624.

Almost surely, 2^21078540 is an apocalyptic number.

21078540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21078540 is an abundant number, since it is smaller than the sum of its proper divisors (51998100).

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

21078540 is a wasteful number, since it uses less digits than its factorization.

21078540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16751 (or 16746 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21078540 is about 4591.1371140492. The cubic root of 21078540 is about 276.2359356216.

The spelling of 21078540 in words is "twenty-one million, seventy-eight thousand, five hundred forty".