84157721 has 8 divisors (see below), whose sum is σ = 86552904. Its totient is φ = 81768960.

The previous prime is 84157709. The next prime is 84157727. The reversal of 84157721 is 12775148.

It can be written as a sum of positive squares in 4 ways, for example, as 50922496 + 33235225 = 7136^2 + 5765^2 .

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 84157721 - 2⁶ = 84157657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (84157727) 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, 39401 + ... + 41481.

It is an arithmetic number, because the mean of its divisors is an integer number (10819113).

Almost surely, 2^84157721 is an apocalyptic number.

It is an amenable number.

84157721 is a deficient number, since it is larger than the sum of its proper divisors (2395183).

84157721 is a wasteful number, since it uses less digits than its factorization.

84157721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3211.

The product of its digits is 15680, while the sum is 35.

The square root of 84157721 is about 9173.7517407002. The cubic root of 84157721 is about 438.2258466352.

The spelling of 84157721 in words is "eighty-four million, one hundred fifty-seven thousand, seven hundred twenty-one".