1285001820 has 120 divisors (see below), whose sum is σ = 4050313344. Its totient is φ = 341034624.

The previous prime is 1285001791. The next prime is 1285001821. The reversal of 1285001820 is 281005821.

1285001820 is a `hidden beast` number, since 128 + 500 + 18 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1285001821) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 359482 + ... + 363038.

Almost surely, 2^1285001820 is an apocalyptic number.

1285001820 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 1285001820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2025156672).

1285001820 is an abundant number, since it is smaller than the sum of its proper divisors (2765311524).

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

1285001820 is a wasteful number, since it uses less digits than its factorization.

1285001820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3801 (or 3790 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 1285001820 is about 35846.9220436009. The cubic root of 1285001820 is about 1087.1794822378.

It can be divided in two parts, 1285001 and 820, that added together give a palindrome (1285821).

The spelling of 1285001820 in words is "one billion, two hundred eighty-five million, one thousand, eight hundred twenty".