1640786221 has 2 divisors, whose sum is σ = 1640786222. Its totient is φ = 1640786220.

The previous prime is 1640786183. The next prime is 1640786227. The reversal of 1640786221 is 1226870461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 903663721 + 737122500 = 30061^2 + 27150^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1640786221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1640786227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 820393110 + 820393111.

It is an arithmetic number, because the mean of its divisors is an integer number (820393111).

Almost surely, 2^1640786221 is an apocalyptic number.

It is an amenable number.

1640786221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1640786221 is an equidigital number, since it uses as much as digits as its factorization.

1640786221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32256, while the sum is 37.

The square root of 1640786221 is about 40506.6194713901. The cubic root of 1640786221 is about 1179.4621270247.

The spelling of 1640786221 in words is "one billion, six hundred forty million, seven hundred eighty-six thousand, two hundred twenty-one".