78721745 has 4 divisors (see below), whose sum is σ = 94466100. Its totient is φ = 62977392.

The previous prime is 78721739. The next prime is 78721751. The reversal of 78721745 is 54712787.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54712787 = 3739 ⋅14633.

It is an interprime number because it is at equal distance from previous prime (78721739) and next prime (78721751).

It can be written as a sum of positive squares in 2 ways, for example, as 52823824 + 25897921 = 7268^2 + 5089^2 .

It is a cyclic number.

It is not a de Polignac number, because 78721745 - 2¹⁰ = 78720721 is a prime.

It is a super-2 number, since 2×78721745² = 12394226271690050, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7872170 + ... + 7872179.

It is an arithmetic number, because the mean of its divisors is an integer number (23616525).

Almost surely, 2^78721745 is an apocalyptic number.

It is an amenable number.

78721745 is a deficient number, since it is larger than the sum of its proper divisors (15744355).

78721745 is a wasteful number, since it uses less digits than its factorization.

78721745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15744354.

The product of its digits is 109760, while the sum is 41.

The square root of 78721745 is about 8872.5275429271. The cubic root of 78721745 is about 428.5796746297.

The spelling of 78721745 in words is "seventy-eight million, seven hundred twenty-one thousand, seven hundred forty-five".