68619721 has 4 divisors (see below), whose sum is σ = 68854212. Its totient is φ = 68385232.

The previous prime is 68619679. The next prime is 68619731. The reversal of 68619721 is 12791686.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 37650496 + 30969225 = 6136^2 + 5565^2 .

It is a cyclic number.

It is not a de Polignac number, because 68619721 - 2⁹ = 68619209 is a prime.

It is a super-2 number, since 2×68619721² = 9417332220235682, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (68619731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 116806 + ... + 117391.

It is an arithmetic number, because the mean of its divisors is an integer number (17213553).

Almost surely, 2^68619721 is an apocalyptic number.

It is an amenable number.

68619721 is a deficient number, since it is larger than the sum of its proper divisors (234491).

68619721 is a wasteful number, since it uses less digits than its factorization.

68619721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 234490.

The product of its digits is 36288, while the sum is 40.

The square root of 68619721 is about 8283.7021312937. The cubic root of 68619721 is about 409.4017071790.

The spelling of 68619721 in words is "sixty-eight million, six hundred nineteen thousand, seven hundred twenty-one".