78729991 has 4 divisors (see below), whose sum is σ = 78857800. Its totient is φ = 78602184.

The previous prime is 78729949. The next prime is 78729997. The reversal of 78729991 is 19992787.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19992787 = 139 ⋅143833.

It is a cyclic number.

It is not a de Polignac number, because 78729991 - 2²¹ = 76632839 is a prime.

It is a super-2 number, since 2×78729991² = 12396822965720162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78729997) 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, 62976 + ... + 64213.

It is an arithmetic number, because the mean of its divisors is an integer number (19714450).

Almost surely, 2^78729991 is an apocalyptic number.

78729991 is a deficient number, since it is larger than the sum of its proper divisors (127809).

78729991 is a wasteful number, since it uses less digits than its factorization.

78729991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127808.

The product of its digits is 571536, while the sum is 52.

The square root of 78729991 is about 8872.9922235963. The cubic root of 78729991 is about 428.5946384943.

The spelling of 78729991 in words is "seventy-eight million, seven hundred twenty-nine thousand, nine hundred ninety-one".