19978081 has 4 divisors (see below), whose sum is σ = 20015152. Its totient is φ = 19941012.

The previous prime is 19978067. The next prime is 19978109. The reversal of 19978081 is 18087991.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19978081 - 2⁷ = 19977953 is a prime.

It is a super-2 number, since 2×19978081² = 798247440885122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19978001) 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, 17715 + ... + 18808.

It is an arithmetic number, because the mean of its divisors is an integer number (5003788).

Almost surely, 2^19978081 is an apocalyptic number.

It is an amenable number.

19978081 is a deficient number, since it is larger than the sum of its proper divisors (37071).

19978081 is an equidigital number, since it uses as much as digits as its factorization.

19978081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37070.

The product of its (nonzero) digits is 36288, while the sum is 43.

The square root of 19978081 is about 4469.6846644926. The cubic root of 19978081 is about 271.3425632123.

The spelling of 19978081 in words is "nineteen million, nine hundred seventy-eight thousand, eighty-one".