70128721 has 8 divisors (see below), whose sum is σ = 75597480. Its totient is φ = 64670592.

The previous prime is 70128719. The next prime is 70128733. The reversal of 70128721 is 12782107.

It can be written as a sum of positive squares in 4 ways, for example, as 7639696 + 62489025 = 2764^2 + 7905^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 70128721 - 2¹ = 70128719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 70128721.

It is not an unprimeable number, because it can be changed into a prime (70128701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15885 + ... + 19813.

It is an arithmetic number, because the mean of its divisors is an integer number (9449685).

Almost surely, 2^70128721 is an apocalyptic number.

It is an amenable number.

70128721 is a deficient number, since it is larger than the sum of its proper divisors (5468759).

70128721 is a wasteful number, since it uses less digits than its factorization.

70128721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5315.

The product of its (nonzero) digits is 1568, while the sum is 28.

The square root of 70128721 is about 8374.2892832765. The cubic root of 70128721 is about 412.3809924216.

The spelling of 70128721 in words is "seventy million, one hundred twenty-eight thousand, seven hundred twenty-one".