1221510820 has 24 divisors (see below), whose sum is σ = 2574649728. Its totient is φ = 486799200.

The previous prime is 1221510799. The next prime is 1221510839. The reversal of 1221510820 is 280151221.

It is a junction number, because it is equal to n+sod(n) for n = 1221510791 and 1221510800.

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, 107266 + ... + 118105.

It is an arithmetic number, because the mean of its divisors is an integer number (107277072).

Almost surely, 2^1221510820 is an apocalyptic number.

1221510820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221510820 is an abundant number, since it is smaller than the sum of its proper divisors (1353138908).

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

1221510820 is a wasteful number, since it uses less digits than its factorization.

1221510820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 225651 (or 225649 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 22.

The square root of 1221510820 is about 34950.1190269790. The cubic root of 1221510820 is about 1068.9706290973.

The spelling of 1221510820 in words is "one billion, two hundred twenty-one million, five hundred ten thousand, eight hundred twenty".