77981121001 has 45 divisors (see below), whose sum is σ = 93921179703. Its totient is φ = 64741551840.

The previous prime is 77981120981. The next prime is 77981121011. The reversal of 77981121001 is 10012118977.

The square root of 77981121001 is 279251.

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

It can be written as a sum of positive squares in only one way, i.e., 3757567401 + 74223553600 = 61299^2 + 272440^2 .

It is not a de Polignac number, because 77981121001 - 2⁵ = 77981120969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77981121011) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 561015190 + ... + 561015328.

Almost surely, 2^77981121001 is an apocalyptic number.

77981121001 is the 279251-st square number.

77981121001 is the 139626-th centered octagonal number.

It is an amenable number.

77981121001 is a deficient number, since it is larger than the sum of its proper divisors (15940058702).

77981121001 is an frugal number, since it uses more digits than its factorization.

77981121001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 187 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 37.

Multiplying 77981121001 by its product of nonzero digits (7056), we get a square (550234789783056 = 23457084²).

Adding to 77981121001 its reverse (10012118977), we get a palindrome (87993239978).

The spelling of 77981121001 in words is "seventy-seven billion, nine hundred eighty-one million, one hundred twenty-one thousand, one".