16620561 has 6 divisors (see below), whose sum is σ = 24007490. Its totient is φ = 11080368.

The previous prime is 16620553. The next prime is 16620587. The reversal of 16620561 is 16502661.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15681600 + 938961 = 3960^2 + 969^2 .

It is not a de Polignac number, because 16620561 - 2³ = 16620553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16620521) 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 5 ways as a sum of consecutive naturals, for example, 923356 + ... + 923373.

Almost surely, 2^16620561 is an apocalyptic number.

It is an amenable number.

16620561 is a deficient number, since it is larger than the sum of its proper divisors (7386929).

16620561 is a wasteful number, since it uses less digits than its factorization.

16620561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1846735 (or 1846732 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 16620561 is about 4076.8322261285. The cubic root of 16620561 is about 255.2007185526.

The spelling of 16620561 in words is "sixteen million, six hundred twenty thousand, five hundred sixty-one".