1621120020 has 96 divisors (see below), whose sum is σ = 4907927808. Its totient is φ = 397443072.

The previous prime is 1621120013. The next prime is 1621120027. The reversal of 1621120020 is 200211261.

It is an interprime number because it is at equal distance from previous prime (1621120013) and next prime (1621120027).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621120027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 196417 + ... + 204503.

It is an arithmetic number, because the mean of its divisors is an integer number (51124248).

Almost surely, 2^1621120020 is an apocalyptic number.

1621120020 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 1621120020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2453963904).

1621120020 is an abundant number, since it is smaller than the sum of its proper divisors (3286807788).

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

1621120020 is a wasteful number, since it uses less digits than its factorization.

1621120020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8369 (or 8367 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 1621120020 is about 40263.1347512833. The cubic root of 1621120020 is about 1174.7308923477.

Adding to 1621120020 its reverse (200211261), we get a palindrome (1821331281).

The spelling of 1621120020 in words is "one billion, six hundred twenty-one million, one hundred twenty thousand, twenty".