78447021 has 4 divisors (see below), whose sum is σ = 104596032. Its totient is φ = 52298012.

The previous prime is 78446999. The next prime is 78447073. The reversal of 78447021 is 12074487.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 78447021 - 2⁵ = 78446989 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78447221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13074501 + ... + 13074506.

It is an arithmetic number, because the mean of its divisors is an integer number (26149008).

Almost surely, 2^78447021 is an apocalyptic number.

It is an amenable number.

78447021 is a deficient number, since it is larger than the sum of its proper divisors (26149011).

78447021 is a wasteful number, since it uses less digits than its factorization.

78447021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26149010.

The product of its (nonzero) digits is 12544, while the sum is 33.

The square root of 78447021 is about 8857.0322907845. The cubic root of 78447021 is about 428.0805395498.

The spelling of 78447021 in words is "seventy-eight million, four hundred forty-seven thousand, twenty-one".