1221855210 has 48 divisors (see below), whose sum is σ = 3181295520. Its totient is φ = 325369440.

The previous prime is 1221855203. The next prime is 1221855223. The reversal of 1221855210 is 125581221.

It is a happy number.

1221855210 is a `hidden beast` number, since 122 + 18 + 5 + 521 + 0 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 57325 + ... + 75695.

It is an arithmetic number, because the mean of its divisors is an integer number (66276990).

Almost surely, 2^1221855210 is an apocalyptic number.

1221855210 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1221855210 is an abundant number, since it is smaller than the sum of its proper divisors (1959440310).

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

1221855210 is a wasteful number, since it uses less digits than its factorization.

1221855210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19123 (or 19120 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 27.

The square root of 1221855210 is about 34955.0455585456. The cubic root of 1221855210 is about 1069.0710807119.

The spelling of 1221855210 in words is "one billion, two hundred twenty-one million, eight hundred fifty-five thousand, two hundred ten".