201821491 has 2 divisors, whose sum is σ = 201821492. Its totient is φ = 201821490.

The previous prime is 201821479. The next prime is 201821519. The reversal of 201821491 is 194128102.

It is an a-pointer prime, because the next prime (201821519) can be obtained adding 201821491 to its sum of digits (28).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 201821491 - 2²¹ = 199724339 is a prime.

It is not a weakly prime, because it can be changed into another prime (201821441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 100910745 + 100910746.

It is an arithmetic number, because the mean of its divisors is an integer number (100910746).

Almost surely, 2^201821491 is an apocalyptic number.

201821491 is a deficient number, since it is larger than the sum of its proper divisors (1).

201821491 is an equidigital number, since it uses as much as digits as its factorization.

201821491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 201821491 is about 14206.3890908281. The cubic root of 201821491 is about 586.5735424172.

Adding to 201821491 its reverse (194128102), we get a palindrome (395949593).

The spelling of 201821491 in words is "two hundred one million, eight hundred twenty-one thousand, four hundred ninety-one".