7640139781 has 4 divisors (see below), whose sum is σ = 7640397472. Its totient is φ = 7639882092.

The previous prime is 7640139769. The next prime is 7640139803. The reversal of 7640139781 is 1879310467.

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 not a de Polignac number, because 7640139781 - 2⁷ = 7640139653 is a prime.

It is a super-2 number, since 2×7640139781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7640139721) 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, 77571 + ... + 145936.

It is an arithmetic number, because the mean of its divisors is an integer number (1910099368).

Almost surely, 2^7640139781 is an apocalyptic number.

It is an amenable number.

7640139781 is a deficient number, since it is larger than the sum of its proper divisors (257691).

7640139781 is a wasteful number, since it uses less digits than its factorization.

7640139781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257690.

The product of its (nonzero) digits is 254016, while the sum is 46.

The square root of 7640139781 is about 87407.8931275660. The cubic root of 7640139781 is about 1969.5504124051.

The spelling of 7640139781 in words is "seven billion, six hundred forty million, one hundred thirty-nine thousand, seven hundred eighty-one".