7778661001 has 4 divisors (see below), whose sum is σ = 7794250000. Its totient is φ = 7763072004.

The previous prime is 7778660951. The next prime is 7778661029. The reversal of 7778661001 is 1001668777.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7778661001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7778661031) 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, 7793751 + ... + 7794748.

It is an arithmetic number, because the mean of its divisors is an integer number (1948562500).

Almost surely, 2^7778661001 is an apocalyptic number.

It is an amenable number.

7778661001 is a deficient number, since it is larger than the sum of its proper divisors (15588999).

7778661001 is a wasteful number, since it uses less digits than its factorization.

7778661001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15588998.

The product of its (nonzero) digits is 98784, while the sum is 43.

The square root of 7778661001 is about 88196.7176316670. The cubic root of 7778661001 is about 1981.3823120333.

The spelling of 7778661001 in words is "seven billion, seven hundred seventy-eight million, six hundred sixty-one thousand, one".