78644551 has 4 divisors (see below), whose sum is σ = 81181504. Its totient is φ = 76107600.

The previous prime is 78644539. The next prime is 78644557. The reversal of 78644551 is 15544687.

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

It is a cyclic number.

It is not a de Polignac number, because 78644551 - 2¹¹ = 78642503 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78644557) 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, 1268430 + ... + 1268491.

It is an arithmetic number, because the mean of its divisors is an integer number (20295376).

Almost surely, 2^78644551 is an apocalyptic number.

78644551 is a deficient number, since it is larger than the sum of its proper divisors (2536953).

78644551 is a wasteful number, since it uses less digits than its factorization.

78644551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2536952.

The product of its digits is 134400, while the sum is 40.

The square root of 78644551 is about 8868.1763063214. The cubic root of 78644551 is about 428.4395413912.

The spelling of 78644551 in words is "seventy-eight million, six hundred forty-four thousand, five hundred fifty-one".