1665090421 has 2 divisors, whose sum is σ = 1665090422. Its totient is φ = 1665090420.

The previous prime is 1665090337. The next prime is 1665090433. The reversal of 1665090421 is 1240905661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1561356196 + 103734225 = 39514^2 + 10185^2 .

It is an emirp because it is prime and its reverse (1240905661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1665090421 - 2⁷ = 1665090293 is a prime.

It is a super-2 number, since 2×1665090421² = 5545052220211914482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665096421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832545210 + 832545211.

It is an arithmetic number, because the mean of its divisors is an integer number (832545211).

Almost surely, 2^1665090421 is an apocalyptic number.

It is an amenable number.

1665090421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665090421 is an equidigital number, since it uses as much as digits as its factorization.

1665090421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 1665090421 is about 40805.5194918531. The cubic root of 1665090421 is about 1185.2572144271.

The spelling of 1665090421 in words is "one billion, six hundred sixty-five million, ninety thousand, four hundred twenty-one".