19891601 has 4 divisors (see below), whose sum is σ = 20376804. Its totient is φ = 19406400.

The previous prime is 19891579. The next prime is 19891631. The reversal of 19891601 is 10619891.

It is a Cunningham number, because it is equal to 4460²+1.

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 960400 + 18931201 = 980^2 + 4351^2 .

It is a cyclic number.

It is not a de Polignac number, because 19891601 - 2¹⁴ = 19875217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19891631) 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, 242540 + ... + 242621.

It is an arithmetic number, because the mean of its divisors is an integer number (5094201).

Almost surely, 2^19891601 is an apocalyptic number.

It is an amenable number.

19891601 is a deficient number, since it is larger than the sum of its proper divisors (485203).

19891601 is an equidigital number, since it uses as much as digits as its factorization.

19891601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 485202.

The product of its (nonzero) digits is 3888, while the sum is 35.

The square root of 19891601 is about 4460.0001121076. Note that the first 3 decimals coincide. The cubic root of 19891601 is about 270.9504727417.

The spelling of 19891601 in words is "nineteen million, eight hundred ninety-one thousand, six hundred one".