16620515521 has 4 divisors (see below), whose sum is σ = 16620813700. Its totient is φ = 16620217344.

The previous prime is 16620515501. The next prime is 16620515533. The reversal of 16620515521 is 12551502661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15665025600 + 955489921 = 125160^2 + 30911^2 .

It is a cyclic number.

It is not a de Polignac number, because 16620515521 - 2⁷ = 16620515393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16620515501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37776 + ... + 186193.

It is an arithmetic number, because the mean of its divisors is an integer number (4155203425).

Almost surely, 2^16620515521 is an apocalyptic number.

It is an amenable number.

16620515521 is a deficient number, since it is larger than the sum of its proper divisors (298179).

16620515521 is an equidigital number, since it uses as much as digits as its factorization.

16620515521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298178.

The product of its (nonzero) digits is 18000, while the sum is 34.

The spelling of 16620515521 in words is "sixteen billion, six hundred twenty million, five hundred fifteen thousand, five hundred twenty-one".