78213389 has 2 divisors, whose sum is σ = 78213390. Its totient is φ = 78213388.

The previous prime is 78213371. The next prime is 78213391. The reversal of 78213389 is 98331287.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74476900 + 3736489 = 8630^2 + 1933^2 .

It is a cyclic number.

It is not a de Polignac number, because 78213389 - 2¹² = 78209293 is a prime.

It is a super-2 number, since 2×78213389² = 12234668437730642, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 78213391, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78213349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39106694 + 39106695.

It is an arithmetic number, because the mean of its divisors is an integer number (39106695).

Almost surely, 2^78213389 is an apocalyptic number.

It is an amenable number.

78213389 is a deficient number, since it is larger than the sum of its proper divisors (1).

78213389 is an equidigital number, since it uses as much as digits as its factorization.

78213389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 41.

The square root of 78213389 is about 8843.8333882994. The cubic root of 78213389 is about 427.6551451755.

The spelling of 78213389 in words is "seventy-eight million, two hundred thirteen thousand, three hundred eighty-nine".