1221011988 has 72 divisors (see below), whose sum is σ = 3403808352. Its totient is φ = 339425856.

The previous prime is 1221011977. The next prime is 1221011999. The reversal of 1221011988 is 8891101221.

It is an interprime number because it is at equal distance from previous prime (1221011977) and next prime (1221011999).

It is a congruent number.

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, 6306 + ... + 49817.

It is an arithmetic number, because the mean of its divisors is an integer number (47275116).

Almost surely, 2^1221011988 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221011988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1701904176).

1221011988 is an abundant number, since it is smaller than the sum of its proper divisors (2182796364).

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

1221011988 is a wasteful number, since it uses less digits than its factorization.

1221011988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56181 (or 56172 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 33.

The square root of 1221011988 is about 34942.9819563242. The cubic root of 1221011988 is about 1068.8250963818.

The spelling of 1221011988 in words is "one billion, two hundred twenty-one million, eleven thousand, nine hundred eighty-eight".