21212380 has 24 divisors (see below), whose sum is σ = 50910048. Its totient is φ = 7272768.

The previous prime is 21212353. The next prime is 21212423. The reversal of 21212380 is 8321212.

21212380 = T₄₇₉ + T₄₈₀ + ... + T₆₁₈.

It is a super-3 number, since 3×21212380³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75619 + ... + 75898.

It is an arithmetic number, because the mean of its divisors is an integer number (2121252).

Almost surely, 2^21212380 is an apocalyptic number.

21212380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212380 is an abundant number, since it is smaller than the sum of its proper divisors (29697668).

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

21212380 is a wasteful number, since it uses less digits than its factorization.

21212380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151533 (or 151531 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21212380 is about 4605.6899591701. The cubic root of 21212380 is about 276.8193637817.

Adding to 21212380 its reverse (8321212), we get a palindrome (29533592).

The spelling of 21212380 in words is "twenty-one million, two hundred twelve thousand, three hundred eighty".