78389621 has 4 divisors (see below), whose sum is σ = 78493932. Its totient is φ = 78285312.

The previous prime is 78389603. The next prime is 78389627. The reversal of 78389621 is 12698387.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12698387 = 13 ⋅976799.

It can be written as a sum of positive squares in 2 ways, for example, as 16200625 + 62188996 = 4025^2 + 7886^2 .

It is a cyclic number.

It is not a de Polignac number, because 78389621 - 2⁶ = 78389557 is a prime.

It is a super-2 number, since 2×78389621² = 12289865361047282, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78389627) 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, 51020 + ... + 52533.

It is an arithmetic number, because the mean of its divisors is an integer number (19623483).

Almost surely, 2^78389621 is an apocalyptic number.

It is an amenable number.

78389621 is a deficient number, since it is larger than the sum of its proper divisors (104311).

78389621 is a wasteful number, since it uses less digits than its factorization.

78389621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104310.

The product of its digits is 145152, while the sum is 44.

The square root of 78389621 is about 8853.7913347899. The cubic root of 78389621 is about 427.9761046577.

The spelling of 78389621 in words is "seventy-eight million, three hundred eighty-nine thousand, six hundred twenty-one".