21221610 has 32 divisors (see below), whose sum is σ = 53929152. Its totient is φ = 5326080.

The previous prime is 21221597. The next prime is 21221621. The reversal of 21221610 is 1612212.

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 21221610.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20296 + ... + 21315.

It is an arithmetic number, because the mean of its divisors is an integer number (1685286).

Almost surely, 2^21221610 is an apocalyptic number.

21221610 is an abundant number, since it is smaller than the sum of its proper divisors (32707542).

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

21221610 is a wasteful number, since it uses less digits than its factorization.

21221610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41638.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21221610 is about 4606.6918716146. The cubic root of 21221610 is about 276.8595081413.

Adding to 21221610 its reverse (1612212), we get a palindrome (22833822).

It can be divided in two parts, 212216 and 10, that added together give a triangular number (212226 = T₆₅₁).

The spelling of 21221610 in words is "twenty-one million, two hundred twenty-one thousand, six hundred ten".