78161721 has 8 divisors (see below), whose sum is σ = 113689824. Its totient is φ = 47370720.

The previous prime is 78161711. The next prime is 78161737. The reversal of 78161721 is 12716187.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 78161721 - 2⁵ = 78161689 is a prime.

It is a super-2 number, since 2×78161721² = 12218509259363682, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33), and also a Moran number because the ratio is a prime number: 2368537 = 78161721 / (7 + 8 + 1 + 6 + 1 + 7 + 2 + 1).

It is not an unprimeable number, because it can be changed into a prime (78161701) 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 7 ways as a sum of consecutive naturals, for example, 1184236 + ... + 1184301.

It is an arithmetic number, because the mean of its divisors is an integer number (14211228).

Almost surely, 2^78161721 is an apocalyptic number.

It is an amenable number.

78161721 is a deficient number, since it is larger than the sum of its proper divisors (35528103).

78161721 is a wasteful number, since it uses less digits than its factorization.

78161721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2368551.

The product of its digits is 4704, while the sum is 33.

The square root of 78161721 is about 8840.9117742459. The cubic root of 78161721 is about 427.5609543399.

The spelling of 78161721 in words is "seventy-eight million, one hundred sixty-one thousand, seven hundred twenty-one".