21081210 has 16 divisors (see below), whose sum is σ = 50594976. Its totient is φ = 5621648.

The previous prime is 21081187. The next prime is 21081211. The reversal of 21081210 is 1218012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21081210.

It is not an unprimeable number, because it can be changed into a prime (21081211) 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, 351324 + ... + 351383.

It is an arithmetic number, because the mean of its divisors is an integer number (3162186).

Almost surely, 2^21081210 is an apocalyptic number.

21081210 is an abundant number, since it is smaller than the sum of its proper divisors (29513766).

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

21081210 is a wasteful number, since it uses less digits than its factorization.

21081210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 702717.

The product of its (nonzero) digits is 32, while the sum is 15.

The square root of 21081210 is about 4591.4278824784. The cubic root of 21081210 is about 276.2475986496.

Adding to 21081210 its reverse (1218012), we get a palindrome (22299222).

The spelling of 21081210 in words is "twenty-one million, eighty-one thousand, two hundred ten".