16621621553 has 12 divisors (see below), whose sum is σ = 17873497908. Its totient is φ = 15449672160.

The previous prime is 16621621547. The next prime is 16621621573. The reversal of 16621621553 is 35512612661.

It can be written as a sum of positive squares in 2 ways, for example, as 11051686129 + 5569935424 = 105127^2 + 74632^2 .

It is not a de Polignac number, because 16621621553 - 2¹⁰ = 16621620529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16621621573) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 415238 + ... + 453503.

It is an arithmetic number, because the mean of its divisors is an integer number (1489458159).

Almost surely, 2^16621621553 is an apocalyptic number.

It is an amenable number.

16621621553 is a deficient number, since it is larger than the sum of its proper divisors (1251876355).

16621621553 is an equidigital number, since it uses as much as digits as its factorization.

16621621553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868832 (or 868813 counting only the distinct ones).

The product of its digits is 64800, while the sum is 38.

The spelling of 16621621553 in words is "sixteen billion, six hundred twenty-one million, six hundred twenty-one thousand, five hundred fifty-three".