78911989 has 8 divisors (see below), whose sum is σ = 85056440. Its totient is φ = 72778176.

The previous prime is 78911981. The next prime is 78911993. The reversal of 78911989 is 98911987.

It can be written as a sum of positive squares in 4 ways, for example, as 731025 + 78180964 = 855^2 + 8842^2 .

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 78911989 - 2³ = 78911981 is a prime.

It is a super-2 number, since 2×78911989² = 12454204015872242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78911981) 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, 19879 + ... + 23515.

It is an arithmetic number, because the mean of its divisors is an integer number (10632055).

Almost surely, 2^78911989 is an apocalyptic number.

It is an amenable number.

78911989 is a deficient number, since it is larger than the sum of its proper divisors (6144451).

78911989 is a wasteful number, since it uses less digits than its factorization.

78911989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5319.

The product of its digits is 326592, while the sum is 52.

The square root of 78911989 is about 8883.2420320511. The cubic root of 78911989 is about 428.9246412333.

The spelling of 78911989 in words is "seventy-eight million, nine hundred eleven thousand, nine hundred eighty-nine".