21172380 has 48 divisors (see below), whose sum is σ = 61200384. Its totient is φ = 5463360.

The previous prime is 21172369. The next prime is 21172381. The reversal of 21172380 is 8327112.

It is a self number, because there is not a number n which added to its sum of digits gives 21172380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172381) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3832 + ... + 7551.

It is an arithmetic number, because the mean of its divisors is an integer number (1275008).

Almost surely, 2^21172380 is an apocalyptic number.

21172380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21172380 is an abundant number, since it is smaller than the sum of its proper divisors (40028004).

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

21172380 is a wasteful number, since it uses less digits than its factorization.

21172380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11426 (or 11424 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21172380 is about 4601.3454554076. The cubic root of 21172380 is about 276.6452556776.

Adding to 21172380 its reverse (8327112), we get a palindrome (29499492).

The spelling of 21172380 in words is "twenty-one million, one hundred seventy-two thousand, three hundred eighty".