78396021 has 36 divisors (see below), whose sum is σ = 125449324. Its totient is φ = 47139840.

The previous prime is 78396013. The next prime is 78396037. The reversal of 78396021 is 12069387.

It can be written as a sum of positive squares in 2 ways, for example, as 30371121 + 48024900 = 5511^2 + 6930^2 .

It is not a de Polignac number, because 78396021 - 2³ = 78396013 is a prime.

It is a super-2 number, since 2×78396021² = 12291872217264882, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78396091) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 209991 + ... + 210363.

Almost surely, 2^78396021 is an apocalyptic number.

It is an amenable number.

78396021 is a deficient number, since it is larger than the sum of its proper divisors (47053303).

78396021 is a wasteful number, since it uses less digits than its factorization.

78396021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594 (or 580 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 78396021 is about 8854.1527544989. The cubic root of 78396021 is about 427.9877514910.

The spelling of 78396021 in words is "seventy-eight million, three hundred ninety-six thousand, twenty-one".