78775921 has 4 divisors (see below), whose sum is σ = 90029632. Its totient is φ = 67522212.

The previous prime is 78775913. The next prime is 78775937. The reversal of 78775921 is 12957787.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12957787 = 2347 ⋅5521.

It is a cyclic number.

It is not a de Polignac number, because 78775921 - 2³ = 78775913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (78775951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5626845 + ... + 5626858.

It is an arithmetic number, because the mean of its divisors is an integer number (22507408).

Almost surely, 2^78775921 is an apocalyptic number.

It is an amenable number.

78775921 is a deficient number, since it is larger than the sum of its proper divisors (11253711).

78775921 is a wasteful number, since it uses less digits than its factorization.

78775921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11253710.

The product of its digits is 246960, while the sum is 46.

The square root of 78775921 is about 8875.5800373835. The cubic root of 78775921 is about 428.6779677089.

The spelling of 78775921 in words is "seventy-eight million, seven hundred seventy-five thousand, nine hundred twenty-one".