68561721 has 14 divisors (see below), whose sum is σ = 102796650. Its totient is φ = 45707328.

The previous prime is 68561719. The next prime is 68561723. The reversal of 68561721 is 12716586.

It is an interprime number because it is at equal distance from previous prime (68561719) and next prime (68561723).

It can be written as a sum of positive squares in only one way, i.e., 67815225 + 746496 = 8235^2 + 864^2 .

It is not a de Polignac number, because 68561721 - 2¹ = 68561719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (68561723) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 46296 + ... + 47753.

Almost surely, 2^68561721 is an apocalyptic number.

It is an amenable number.

68561721 is a deficient number, since it is larger than the sum of its proper divisors (34234929).

68561721 is an frugal number, since it uses more digits than its factorization.

68561721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94067 (or 94052 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 68561721 is about 8280.2005410497. The cubic root of 68561721 is about 409.2863273632.

The spelling of 68561721 in words is "sixty-eight million, five hundred sixty-one thousand, seven hundred twenty-one".