1621116720 has 80 divisors (see below), whose sum is σ = 5583853920. Its totient is φ = 432297216.

The previous prime is 1621116709. The next prime is 1621116799. The reversal of 1621116720 is 276111261.

It is a happy number.

1621116720 is a `hidden beast` number, since 1 + 621 + 1 + 16 + 7 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (80).

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 373099 + ... + 377418.

It is an arithmetic number, because the mean of its divisors is an integer number (69798174).

Almost surely, 2^1621116720 is an apocalyptic number.

1621116720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1621116720 is an abundant number, since it is smaller than the sum of its proper divisors (3962737200).

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

1621116720 is a wasteful number, since it uses less digits than its factorization.

1621116720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750539 (or 750527 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 1621116720 is about 40263.0937708468. The cubic root of 1621116720 is about 1174.7300952415.

Adding to 1621116720 its reverse (276111261), we get a palindrome (1897227981).

It can be divided in two parts, 1621 and 116720, that added together give a triangular number (118341 = T₄₈₆).

The spelling of 1621116720 in words is "one billion, six hundred twenty-one million, one hundred sixteen thousand, seven hundred twenty".