78345021 has 16 divisors (see below), whose sum is σ = 108805248. Its totient is φ = 50097600.

The previous prime is 78345019. The next prime is 78345031. The reversal of 78345021 is 12054387.

It is not a de Polignac number, because 78345021 - 2¹ = 78345019 is a prime.

It is a super-2 number, since 2×78345021² = 12275884630980882, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 78345021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78345031) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2911 + ... + 12851.

It is an arithmetic number, because the mean of its divisors is an integer number (6800328).

Almost surely, 2^78345021 is an apocalyptic number.

78345021 is a gapful number since it is divisible by the number (71) formed by its first and last digit.

It is an amenable number.

78345021 is a deficient number, since it is larger than the sum of its proper divisors (30460227).

78345021 is a wasteful number, since it uses less digits than its factorization.

78345021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10052.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 78345021 is about 8851.2722814294. The cubic root of 78345021 is about 427.8949231817.

The spelling of 78345021 in words is "seventy-eight million, three hundred forty-five thousand, twenty-one".