21078240 has 48 divisors (see below), whose sum is σ = 66397968. Its totient is φ = 5620736.

The previous prime is 21078209. The next prime is 21078257. The reversal of 21078240 is 4287012.

It is a tau number, because it is divible by the number of its divisors (48).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21078240.

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, 21477 + ... + 22436.

It is an arithmetic number, because the mean of its divisors is an integer number (1383291).

Almost surely, 2^21078240 is an apocalyptic number.

21078240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21078240 is an abundant number, since it is smaller than the sum of its proper divisors (45319728).

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

21078240 is a wasteful number, since it uses less digits than its factorization.

21078240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43931 (or 43923 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21078240 is about 4591.1044422884. The cubic root of 21078240 is about 276.2346251075.

The spelling of 21078240 in words is "twenty-one million, seventy-eight thousand, two hundred forty".