78459921 has 10 divisors (see below), whose sum is σ = 117205682. Its totient is φ = 52306560.

The previous prime is 78459893. The next prime is 78459989. The reversal of 78459921 is 12995487.

It can be written as a sum of positive squares in only one way, i.e., 41990400 + 36469521 = 6480^2 + 6039^2 .

It is not a de Polignac number, because 78459921 - 2²² = 74265617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78459991) 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 9 ways as a sum of consecutive naturals, for example, 484240 + ... + 484401.

Almost surely, 2^78459921 is an apocalyptic number.

It is an amenable number.

78459921 is a deficient number, since it is larger than the sum of its proper divisors (38745761).

78459921 is an equidigital number, since it uses as much as digits as its factorization.

78459921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 968653 (or 968644 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 78459921 is about 8857.7604957461. The cubic root of 78459921 is about 428.1040030976.

It can be divided in two parts, 7845 and 9921, that added together give a triangular number (17766 = T₁₈₈).

The spelling of 78459921 in words is "seventy-eight million, four hundred fifty-nine thousand, nine hundred twenty-one".