21171380 has 24 divisors (see below), whose sum is σ = 45301032. Its totient is φ = 8308352.

The previous prime is 21171379. The next prime is 21171401. The reversal of 21171380 is 8317112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2835856 + 18335524 = 1684^2 + 4282^2 .

It is a super-2 number, since 2×21171380² = 896454662208800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8927 + ... + 11046.

It is an arithmetic number, because the mean of its divisors is an integer number (1887543).

Almost surely, 2^21171380 is an apocalyptic number.

21171380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21171380 is an abundant number, since it is smaller than the sum of its proper divisors (24129652).

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

21171380 is a wasteful number, since it uses less digits than its factorization.

21171380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20035 (or 20033 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 21171380 is about 4601.2367902554. The cubic root of 21171380 is about 276.6409001665.

Adding to 21171380 its reverse (8317112), we get a palindrome (29488492).

The spelling of 21171380 in words is "twenty-one million, one hundred seventy-one thousand, three hundred eighty".