1640654657 has 4 divisors (see below), whose sum is σ = 1646577876. Its totient is φ = 1634731440.

The previous prime is 1640654651. The next prime is 1640654677. The reversal of 1640654657 is 7564560461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 216648961 + 1424005696 = 14719^2 + 37736^2 .

It is a cyclic number.

It is not a de Polignac number, because 1640654657 - 2¹⁴ = 1640638273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640654651) 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, 2961194 + ... + 2961747.

It is an arithmetic number, because the mean of its divisors is an integer number (411644469).

Almost surely, 2^1640654657 is an apocalyptic number.

It is an amenable number.

1640654657 is a deficient number, since it is larger than the sum of its proper divisors (5923219).

1640654657 is an equidigital number, since it uses as much as digits as its factorization.

1640654657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5923218.

The product of its (nonzero) digits is 604800, while the sum is 44.

The square root of 1640654657 is about 40504.9954573507. The cubic root of 1640654657 is about 1179.4306017106.

The spelling of 1640654657 in words is "one billion, six hundred forty million, six hundred fifty-four thousand, six hundred fifty-seven".