1671687821 has 2 divisors, whose sum is σ = 1671687822. Its totient is φ = 1671687820.

The previous prime is 1671687781. The next prime is 1671687833. The reversal of 1671687821 is 1287861761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 960132196 + 711555625 = 30986^2 + 26675^2 .

It is a cyclic number.

It is not a de Polignac number, because 1671687821 - 2¹⁸ = 1671425677 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1671687841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 835843910 + 835843911.

It is an arithmetic number, because the mean of its divisors is an integer number (835843911).

Almost surely, 2^1671687821 is an apocalyptic number.

It is an amenable number.

1671687821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1671687821 is an equidigital number, since it uses as much as digits as its factorization.

1671687821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 225792, while the sum is 47.

The square root of 1671687821 is about 40886.2791288227. The cubic root of 1671687821 is about 1186.8205551577.

The spelling of 1671687821 in words is "one billion, six hundred seventy-one million, six hundred eighty-seven thousand, eight hundred twenty-one".