501531659721 has 9 divisors (see below), whose sum is σ = 724437688429. Its totient is φ = 334353023436.

The previous prime is 501531659689. The next prime is 501531659773. The reversal of 501531659721 is 127956135105.

The square root of 501531659721 is 708189.

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

501531659721 is a `hidden beast` number, since 5 + 0 + 1 + 5 + 31 + 6 + 597 + 21 = 666.

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

It is not a de Polignac number, because 501531659721 - 2⁵ = 501531659689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (501531609721) 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, 2006536 + ... + 2242598.

Almost surely, 2^501531659721 is an apocalyptic number.

501531659721 is the 708189-th square number.

501531659721 is the 354095-th centered octagonal number.

It is an amenable number.

501531659721 is a deficient number, since it is larger than the sum of its proper divisors (222906028708).

501531659721 is an frugal number, since it uses more digits than its factorization.

501531659721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 472132 (or 236066 counting only the distinct ones).

The product of its (nonzero) digits is 283500, while the sum is 45.

The spelling of 501531659721 in words is "five hundred one billion, five hundred thirty-one million, six hundred fifty-nine thousand, seven hundred twenty-one".