19855561 has 16 divisors (see below), whose sum is σ = 22284288. Its totient is φ = 17539200.

The previous prime is 19855559. The next prime is 19855567. The reversal of 19855561 is 16555891.

It is a cyclic number.

It is not a de Polignac number, because 19855561 - 2¹ = 19855559 is a prime.

It is a Duffinian number.

Its product of digits (54000) is a multiple of the sum of its prime divisors (432).

It is not an unprimeable number, because it can be changed into a prime (19855567) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 85101 + ... + 85333.

It is an arithmetic number, because the mean of its divisors is an integer number (1392768).

Almost surely, 2^19855561 is an apocalyptic number.

19855561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19855561 is a deficient number, since it is larger than the sum of its proper divisors (2428727).

19855561 is a wasteful number, since it uses less digits than its factorization.

19855561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432.

The product of its digits is 54000, while the sum is 40.

The square root of 19855561 is about 4455.9579217044. The cubic root of 19855561 is about 270.7867359886.

The spelling of 19855561 in words is "nineteen million, eight hundred fifty-five thousand, five hundred sixty-one".