21078456 has 64 divisors (see below), whose sum is σ = 61870080. Its totient is φ = 5857920.

The previous prime is 21078451. The next prime is 21078457. The reversal of 21078456 is 65487012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078451) 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, 4521 + ... + 7911.

It is an arithmetic number, because the mean of its divisors is an integer number (966720).

Almost surely, 2^21078456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21078456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30935040).

21078456 is an abundant number, since it is smaller than the sum of its proper divisors (40791624).

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

21078456 is a wasteful number, since it uses less digits than its factorization.

21078456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3444 (or 3440 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21078456 is about 4591.1279659796. The cubic root of 21078456 is about 276.2355686789.

The spelling of 21078456 in words is "twenty-one million, seventy-eight thousand, four hundred fifty-six".