21528378 has 24 divisors (see below), whose sum is σ = 46894068. Its totient is φ = 7137792.

The previous prime is 21528371. The next prime is 21528379. The reversal of 21528378 is 87382512.

It can be written as a sum of positive squares in 2 ways, for example, as 20766249 + 762129 = 4557^2 + 873^2 .

It is a super-3 number, since 3×21528378³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21528371) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 376 + ... + 6572.

Almost surely, 2^21528378 is an apocalyptic number.

21528378 is an abundant number, since it is smaller than the sum of its proper divisors (25365690).

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

21528378 is a wasteful number, since it uses less digits than its factorization.

21528378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6398 (or 6395 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 21528378 is about 4639.8683170969. The cubic root of 21528378 is about 278.1871744684.

The spelling of 21528378 in words is "twenty-one million, five hundred twenty-eight thousand, three hundred seventy-eight".