78809989 has 2 divisors, whose sum is σ = 78809990. Its totient is φ = 78809988.

The previous prime is 78809981. The next prime is 78809999. The reversal of 78809989 is 98990887.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71064900 + 7745089 = 8430^2 + 2783^2 .

It is a cyclic number.

It is not a de Polignac number, because 78809989 - 2³ = 78809981 is a prime.

It is a super-2 number, since 2×78809989² = 12422028732360242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78809981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39404994 + 39404995.

It is an arithmetic number, because the mean of its divisors is an integer number (39404995).

Almost surely, 2^78809989 is an apocalyptic number.

It is an amenable number.

78809989 is a deficient number, since it is larger than the sum of its proper divisors (1).

78809989 is an equidigital number, since it uses as much as digits as its factorization.

78809989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2612736, while the sum is 58.

The square root of 78809989 is about 8877.4990284426. The cubic root of 78809989 is about 428.7397551859.

The spelling of 78809989 in words is "seventy-eight million, eight hundred nine thousand, nine hundred eighty-nine".