21078464 has 56 divisors (see below), whose sum is σ = 46329600. Its totient is φ = 9434880.

The previous prime is 21078461. The next prime is 21078509. The reversal of 21078464 is 46487012.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 21078464.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078461) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55427 + ... + 55805.

Almost surely, 2^21078464 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 21078464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23164800).

21078464 is an abundant number, since it is smaller than the sum of its proper divisors (25251136).

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

21078464 is a wasteful number, since it uses less digits than its factorization.

21078464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 481 (or 471 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 21078464 is about 4591.1288372251. The cubic root of 21078464 is about 276.2356036259.

The spelling of 21078464 in words is "twenty-one million, seventy-eight thousand, four hundred sixty-four".