21021001220 has 48 divisors (see below), whose sum is σ = 44426188800. Its totient is φ = 8354828160.

The previous prime is 21021001213. The next prime is 21021001231. The reversal of 21021001220 is 2210012012.

It is a happy number.

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, 2285030 + ... + 2294210.

It is an arithmetic number, because the mean of its divisors is an integer number (925545600).

Almost surely, 2^21021001220 is an apocalyptic number.

21021001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021001220 is an abundant number, since it is smaller than the sum of its proper divisors (23405187580).

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

21021001220 is a wasteful number, since it uses less digits than its factorization.

21021001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9908 (or 9906 counting only the distinct ones).

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

Adding to 21021001220 its reverse (2210012012), we get a palindrome (23231013232).

The spelling of 21021001220 in words is "twenty-one billion, twenty-one million, one thousand, two hundred twenty".