128102721 has 4 divisors (see below), whose sum is σ = 170803632. Its totient is φ = 85401812.

The previous prime is 128102717. The next prime is 128102743. The reversal of 128102721 is 127201821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127201821 = 3 ⋅42400607.

It is a cyclic number.

It is not a de Polignac number, because 128102721 - 2² = 128102717 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 128102691 and 128102700.

It is not an unprimeable number, because it can be changed into a prime (128102791) 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, 21350451 + ... + 21350456.

It is an arithmetic number, because the mean of its divisors is an integer number (42700908).

Almost surely, 2^128102721 is an apocalyptic number.

It is an amenable number.

128102721 is a deficient number, since it is larger than the sum of its proper divisors (42700911).

128102721 is an equidigital number, since it uses as much as digits as its factorization.

128102721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42700910.

The product of its (nonzero) digits is 448, while the sum is 24.

The square root of 128102721 is about 11318.2472582993. The cubic root of 128102721 is about 504.1031967760.

The spelling of 128102721 in words is "one hundred twenty-eight million, one hundred two thousand, seven hundred twenty-one".