1640978 has 4 divisors (see below), whose sum is σ = 2461470. Its totient is φ = 820488.

The previous prime is 1640971. The next prime is 1641007. The reversal of 1640978 is 8790461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8790461 = 631 ⋅13931.

It can be written as a sum of positive squares in only one way, i.e., 1620529 + 20449 = 1273^2 + 143^2 .

It is not an unprimeable number, because it can be changed into a prime (1640971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410243 + ... + 410246.

2^1640978 is an apocalyptic number.

1640978 is a deficient number, since it is larger than the sum of its proper divisors (820492).

1640978 is an equidigital number, since it uses as much as digits as its factorization.

1640978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820491.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 1640978 is about 1281.0066354239. The cubic root of 1640978 is about 117.9508078015.

The spelling of 1640978 in words is "one million, six hundred forty thousand, nine hundred seventy-eight".