21530778 has 16 divisors (see below), whose sum is σ = 43108416. Its totient is φ = 7169120.

The previous prime is 21530777. The next prime is 21530779. The reversal of 21530778 is 87703512.

It is an interprime number because it is at equal distance from previous prime (21530777) and next prime (21530779).

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21530777) 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, 7675 + ... + 10097.

It is an arithmetic number, because the mean of its divisors is an integer number (2694276).

Almost surely, 2^21530778 is an apocalyptic number.

21530778 is an abundant number, since it is smaller than the sum of its proper divisors (21577638).

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

21530778 is a wasteful number, since it uses less digits than its factorization.

21530778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3909.

The product of its (nonzero) digits is 11760, while the sum is 33.

The square root of 21530778 is about 4640.1269379188. The cubic root of 21530778 is about 278.1975115904.

The spelling of 21530778 in words is "twenty-one million, five hundred thirty thousand, seven hundred seventy-eight".