621320721121 has 27 divisors (see below), whose sum is σ = 666211466361. Its totient is φ = 579336747264.

The previous prime is 621320721113. The next prime is 621320721127. The reversal of 621320721121 is 121127023126.

The square root of 621320721121 is 788239.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 313679521 + 621007041600 = 17711^2 + 788040^2 .

It is not a de Polignac number, because 621320721121 - 2³ = 621320721113 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 621320721121.

It is not an unprimeable number, because it can be changed into a prime (621320721127) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 2666612421 + ... + 2666612653.

Almost surely, 2^621320721121 is an apocalyptic number.

621320721121 is the 788239-th square number.

621320721121 is the 394120-th centered octagonal number.

It is an amenable number.

621320721121 is a deficient number, since it is larger than the sum of its proper divisors (44890745240).

621320721121 is an frugal number, since it uses more digits than its factorization.

621320721121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 898 (or 449 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

Adding to 621320721121 its reverse (121127023126), we get a palindrome (742447744247).

The spelling of 621320721121 in words is "six hundred twenty-one billion, three hundred twenty million, seven hundred twenty-one thousand, one hundred twenty-one".