21210001220 has 24 divisors (see below), whose sum is σ = 44548502208. Its totient is φ = 8482572000.

The previous prime is 21210001151. The next prime is 21210001289. The reversal of 21210001220 is 2210001212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21210001151) and next prime (21210001289).

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, 36815 + ... + 209225.

It is an arithmetic number, because the mean of its divisors is an integer number (1856187592).

Almost surely, 2^21210001220 is an apocalyptic number.

21210001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21210001220 is an abundant number, since it is smaller than the sum of its proper divisors (23338500988).

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

21210001220 is a wasteful number, since it uses less digits than its factorization.

21210001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178571 (or 178569 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21210001220 its reverse (2210001212), we get a palindrome (23420002432).

The spelling of 21210001220 in words is "twenty-one billion, two hundred ten million, one thousand, two hundred twenty".