78388421 has 4 divisors (see below), whose sum is σ = 81091500. Its totient is φ = 75685344.

The previous prime is 78388417. The next prime is 78388447. The reversal of 78388421 is 12488387.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 65529025 + 12859396 = 8095^2 + 3586^2 .

It is a cyclic number.

It is not a de Polignac number, because 78388421 - 2² = 78388417 is a prime.

It is a super-2 number, since 2×78388421² = 12289489093746482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78381421) 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, 1351496 + ... + 1351553.

It is an arithmetic number, because the mean of its divisors is an integer number (20272875).

Almost surely, 2^78388421 is an apocalyptic number.

It is an amenable number.

78388421 is a deficient number, since it is larger than the sum of its proper divisors (2703079).

78388421 is a wasteful number, since it uses less digits than its factorization.

78388421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2703078.

The product of its digits is 86016, while the sum is 41.

The square root of 78388421 is about 8853.7235669519. The cubic root of 78388421 is about 427.9739208059.

The spelling of 78388421 in words is "seventy-eight million, three hundred eighty-eight thousand, four hundred twenty-one".