21147920 has 20 divisors (see below), whose sum is σ = 49169100. Its totient is φ = 8459136.

The previous prime is 21147869. The next prime is 21147937. The reversal of 21147920 is 2974112.

It can be written as a sum of positive squares in 2 ways, for example, as 2347024 + 18800896 = 1532^2 + 4336^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 21147920.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132095 + ... + 132254.

It is an arithmetic number, because the mean of its divisors is an integer number (2458455).

Almost surely, 2^21147920 is an apocalyptic number.

21147920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21147920 is an abundant number, since it is smaller than the sum of its proper divisors (28021180).

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

21147920 is a wasteful number, since it uses less digits than its factorization.

21147920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264362 (or 264356 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21147920 is about 4598.6867690679. The cubic root of 21147920 is about 276.5386805004.

The spelling of 21147920 in words is "twenty-one million, one hundred forty-seven thousand, nine hundred twenty".