76421721781 has 2 divisors, whose sum is σ = 76421721782. Its totient is φ = 76421721780.

The previous prime is 76421721769. The next prime is 76421721821. The reversal of 76421721781 is 18712712467.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54468558225 + 21953163556 = 233385^2 + 148166^2 .

It is an emirp because it is prime and its reverse (18712712467) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 76421721781 - 2¹⁷ = 76421590709 is a prime.

It is a super-2 number, since 2×76421721781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (76421721731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38210860890 + 38210860891.

It is an arithmetic number, because the mean of its divisors is an integer number (38210860891).

Almost surely, 2^76421721781 is an apocalyptic number.

It is an amenable number.

76421721781 is a deficient number, since it is larger than the sum of its proper divisors (1).

76421721781 is an equidigital number, since it uses as much as digits as its factorization.

76421721781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 263424, while the sum is 46.

The spelling of 76421721781 in words is "seventy-six billion, four hundred twenty-one million, seven hundred twenty-one thousand, seven hundred eighty-one".