78398821 has 2 divisors, whose sum is σ = 78398822. Its totient is φ = 78398820.

The previous prime is 78398813. The next prime is 78398843. The reversal of 78398821 is 12889387.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40132225 + 38266596 = 6335^2 + 6186^2 .

It is a cyclic number.

It is not a de Polignac number, because 78398821 - 2³ = 78398813 is a prime.

It is a super-2 number, since 2×78398821² = 12292750268380082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78398851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39199410 + 39199411.

It is an arithmetic number, because the mean of its divisors is an integer number (39199411).

Almost surely, 2^78398821 is an apocalyptic number.

It is an amenable number.

78398821 is a deficient number, since it is larger than the sum of its proper divisors (1).

78398821 is an equidigital number, since it uses as much as digits as its factorization.

78398821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 46.

The square root of 78398821 is about 8854.3108709826. The cubic root of 78398821 is about 427.9928467812.

The spelling of 78398821 in words is "seventy-eight million, three hundred ninety-eight thousand, eight hundred twenty-one".