78047921 has 4 divisors (see below), whose sum is σ = 89197632. Its totient is φ = 66898212.

The previous prime is 78047909. The next prime is 78047923. The reversal of 78047921 is 12974087.

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 78047921 - 2¹⁰ = 78046897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78047923) 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, 5574845 + ... + 5574858.

It is an arithmetic number, because the mean of its divisors is an integer number (22299408).

Almost surely, 2^78047921 is an apocalyptic number.

It is an amenable number.

78047921 is a deficient number, since it is larger than the sum of its proper divisors (11149711).

78047921 is a wasteful number, since it uses less digits than its factorization.

78047921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11149710.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 78047921 is about 8834.4734421470. The cubic root of 78047921 is about 427.3533502895.

The spelling of 78047921 in words is "seventy-eight million, forty-seven thousand, nine hundred twenty-one".