19905681 has 8 divisors (see below), whose sum is σ = 26642880. Its totient is φ = 13219472.

The previous prime is 19905679. The next prime is 19905701. The reversal of 19905681 is 18650991.

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 19905681 - 2¹ = 19905679 is a prime.

It is a super-2 number, since 2×19905681² = 792472272147522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19905481) 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, 11826 + ... + 13403.

It is an arithmetic number, because the mean of its divisors is an integer number (3330360).

Almost surely, 2^19905681 is an apocalyptic number.

It is an amenable number.

19905681 is a deficient number, since it is larger than the sum of its proper divisors (6737199).

19905681 is a wasteful number, since it uses less digits than its factorization.

19905681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25495.

The product of its (nonzero) digits is 19440, while the sum is 39.

The square root of 19905681 is about 4461.5783081775. The cubic root of 19905681 is about 271.0143872029.

The spelling of 19905681 in words is "nineteen million, nine hundred five thousand, six hundred eighty-one".