78127921 has 3 divisors (see below), whose sum is σ = 78136761. Its totient is φ = 78119082.

The previous prime is 78127909. The next prime is 78128003. The reversal of 78127921 is 12972187.

The square root of 78127921 is 8839.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12972187 = 277 ⋅46831.

It is not a de Polignac number, because 78127921 - 2⁷ = 78127793 is a prime.

It is a super-2 number, since 2×78127921² = 12207944079564482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78127901) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 4420 + ... + 13258.

It is an arithmetic number, because the mean of its divisors is an integer number (26045587).

Almost surely, 2^78127921 is an apocalyptic number.

78127921 is the 8839-th square number.

78127921 is the 4420-th centered octagonal number.

It is an amenable number.

78127921 is a deficient number, since it is larger than the sum of its proper divisors (8840).

78127921 is an frugal number, since it uses more digits than its factorization.

78127921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17678 (or 8839 counting only the distinct ones).

The product of its digits is 14112, while the sum is 37.

The cubic root of 78127921 is about 427.4993144318.

The spelling of 78127921 in words is "seventy-eight million, one hundred twenty-seven thousand, nine hundred twenty-one".