1621855872 has 448 divisors, whose sum is σ = 5993487360. Its totient is φ = 425502720.

The previous prime is 1621855871. The next prime is 1621855877. The reversal of 1621855872 is 2785581261.

1621855872 is a `hidden beast` number, since 1 + 6 + 21 + 8 + 558 + 72 = 666.

It is a tau number, because it is divible by the number of its divisors (448).

It is not an unprimeable number, because it can be changed into a prime (1621855871) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 8491297 + ... + 8491487.

It is an arithmetic number, because the mean of its divisors is an integer number (13378320).

Almost surely, 2^1621855872 is an apocalyptic number.

1621855872 is a gapful number since it is divisible by the number (12) 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 1621855872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2996743680).

1621855872 is an abundant number, since it is smaller than the sum of its proper divisors (4371631488).

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

1621855872 is an equidigital number, since it uses as much as digits as its factorization.

1621855872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243 (or 216 counting only the distinct ones).

The product of its digits is 268800, while the sum is 45.

The square root of 1621855872 is about 40272.2717511689. The cubic root of 1621855872 is about 1174.9086084342.

The spelling of 1621855872 in words is "one billion, six hundred twenty-one million, eight hundred fifty-five thousand, eight hundred seventy-two".