1211551000 has 128 divisors (see below), whose sum is σ = 3132380160. Its totient is φ = 434928000.

The previous prime is 1211550971. The next prime is 1211551111. The reversal of 1211551000 is 1551121.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 912337 + ... + 913663.

It is an arithmetic number, because the mean of its divisors is an integer number (24471720).

Almost surely, 2^1211551000 is an apocalyptic number.

1211551000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1211551000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1566190080).

1211551000 is an abundant number, since it is smaller than the sum of its proper divisors (1920829160).

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

1211551000 is a wasteful number, since it uses less digits than its factorization.

1211551000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1442 (or 1428 counting only the distinct ones).

The product of its (nonzero) digits is 50, while the sum is 16.

The square root of 1211551000 is about 34807.3411796994. The cubic root of 1211551000 is about 1066.0573451405.

The spelling of 1211551000 in words is "one billion, two hundred eleven million, five hundred fifty-one thousand".