19906561 has 8 divisors (see below), whose sum is σ = 20220200. Its totient is φ = 19595520.

The previous prime is 19906553. The next prime is 19906577. The reversal of 19906561 is 16560991.

It can be written as a sum of positive squares in 4 ways, for example, as 59536 + 19847025 = 244^2 + 4455^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19906561 - 2³ = 19906553 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 19906561.

It is not an unprimeable number, because it can be changed into a prime (19906531) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19225 + ... + 20233.

It is an arithmetic number, because the mean of its divisors is an integer number (2527525).

It is a Proth number, since it is equal to 1215 ⋅ 2¹⁴ + 1 and 1215 < 2¹⁴.

Almost surely, 2^19906561 is an apocalyptic number.

It is an amenable number.

19906561 is a deficient number, since it is larger than the sum of its proper divisors (313639).

19906561 is a wasteful number, since it uses less digits than its factorization.

19906561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1299.

The product of its (nonzero) digits is 14580, while the sum is 37.

The square root of 19906561 is about 4461.6769268964. The cubic root of 19906561 is about 271.0183808559.

The spelling of 19906561 in words is "nineteen million, nine hundred six thousand, five hundred sixty-one".