1621998720 has 192 divisors, whose sum is σ = 5623300800. Its totient is φ = 430811136.

The previous prime is 1621998701. The next prime is 1621998727. The reversal of 1621998720 is 278991261.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1621998727) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 2182669 + ... + 2183411.

It is an arithmetic number, because the mean of its divisors is an integer number (29288025).

Almost surely, 2^1621998720 is an apocalyptic number.

1621998720 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 1621998720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2811650400).

1621998720 is an abundant number, since it is smaller than the sum of its proper divisors (4001302080).

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

1621998720 is a wasteful number, since it uses less digits than its factorization.

1621998720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1147 (or 1132 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 1621998720 is about 40274.0452400799. The cubic root of 1621998720 is about 1174.9431015152.

The spelling of 1621998720 in words is "one billion, six hundred twenty-one million, nine hundred ninety-eight thousand, seven hundred twenty".