4331087721 has 9 divisors (see below), whose sum is σ = 6256300791. Its totient is φ = 2887260192.

The previous prime is 4331087707. The next prime is 4331087729. The reversal of 4331087721 is 1277801334.

The square root of 4331087721 is 65811.

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

It can be written as a sum of positive squares in only one way, i.e., 699338025 + 3631749696 = 26445^2 + 60264^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 4331087721 - 2¹⁵ = 4331054953 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (4331087729) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 186465 + ... + 208401.

Almost surely, 2^4331087721 is an apocalyptic number.

4331087721 is the 65811-st square number.

4331087721 is the 32906-th centered octagonal number.

It is an amenable number.

4331087721 is a deficient number, since it is larger than the sum of its proper divisors (1925213070).

4331087721 is an frugal number, since it uses more digits than its factorization.

4331087721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43880 (or 21940 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 36.

The cubic root of 4331087721 is about 1630.0427455638.

Multiplying 4331087721 by its sum of digits (36), we get a square (155919157956 = 394866²).

Multiplying 4331087721 by its product of nonzero digits (28224), we get a square (122240619837504 = 11056248²).

The spelling of 4331087721 in words is "four billion, three hundred thirty-one million, eighty-seven thousand, seven hundred twenty-one".