78218551 has 4 divisors (see below), whose sum is σ = 79290112. Its totient is φ = 77146992.

The previous prime is 78218537. The next prime is 78218557. The reversal of 78218551 is 15581287.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15581287 = 269 ⋅57923.

It is a cyclic number.

It is not a de Polignac number, because 78218551 - 2⁹ = 78218039 is a prime.

It is a super-2 number, since 2×78218551² = 12236283441079202, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 78218551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78218557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 535671 + ... + 535816.

It is an arithmetic number, because the mean of its divisors is an integer number (19822528).

Almost surely, 2^78218551 is an apocalyptic number.

78218551 is a deficient number, since it is larger than the sum of its proper divisors (1071561).

78218551 is a wasteful number, since it uses less digits than its factorization.

78218551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1071560.

The product of its digits is 22400, while the sum is 37.

The square root of 78218551 is about 8844.1252252555. The cubic root of 78218551 is about 427.6645532293.

The spelling of 78218551 in words is "seventy-eight million, two hundred eighteen thousand, five hundred fifty-one".