67721021 has 2 divisors, whose sum is σ = 67721022. Its totient is φ = 67721020.

The previous prime is 67721011. The next prime is 67721057. The reversal of 67721021 is 12012776.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65205625 + 2515396 = 8075^2 + 1586^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67721021 is a prime.

It is a super-2 number, since 2×67721021² = 9172273370564882, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (67721011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33860510 + 33860511.

It is an arithmetic number, because the mean of its divisors is an integer number (33860511).

Almost surely, 2^67721021 is an apocalyptic number.

It is an amenable number.

67721021 is a deficient number, since it is larger than the sum of its proper divisors (1).

67721021 is an equidigital number, since it uses as much as digits as its factorization.

67721021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1176, while the sum is 26.

The square root of 67721021 is about 8229.2782794119. The cubic root of 67721021 is about 407.6065607629.

Adding to 67721021 its reverse (12012776), we get a palindrome (79733797).

The spelling of 67721021 in words is "sixty-seven million, seven hundred twenty-one thousand, twenty-one".