78197421 has 4 divisors (see below), whose sum is σ = 104263232. Its totient is φ = 52131612.

The previous prime is 78197417. The next prime is 78197429. The reversal of 78197421 is 12479187.

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 not a de Polignac number, because 78197421 - 2² = 78197417 is a prime.

It is a super-2 number, since 2×78197421² = 12229673302102482, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 78197421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78197429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13032901 + ... + 13032906.

It is an arithmetic number, because the mean of its divisors is an integer number (26065808).

Almost surely, 2^78197421 is an apocalyptic number.

It is an amenable number.

78197421 is a deficient number, since it is larger than the sum of its proper divisors (26065811).

78197421 is a wasteful number, since it uses less digits than its factorization.

78197421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26065810.

The product of its digits is 28224, while the sum is 39.

The square root of 78197421 is about 8842.9305662772. The cubic root of 78197421 is about 427.6260399195.

The spelling of 78197421 in words is "seventy-eight million, one hundred ninety-seven thousand, four hundred twenty-one".