19901641 has 2 divisors, whose sum is σ = 19901642. Its totient is φ = 19901640.

The previous prime is 19901639. The next prime is 19901663. The reversal of 19901641 is 14610991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17606416 + 2295225 = 4196^2 + 1515^2 .

It is an emirp because it is prime and its reverse (14610991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19901641 - 2¹ = 19901639 is a prime.

Together with 19901639, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (19901681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9950820 + 9950821.

It is an arithmetic number, because the mean of its divisors is an integer number (9950821).

Almost surely, 2^19901641 is an apocalyptic number.

It is an amenable number.

19901641 is a deficient number, since it is larger than the sum of its proper divisors (1).

19901641 is an equidigital number, since it uses as much as digits as its factorization.

19901641 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 19901641 is about 4461.1255306257. The cubic root of 19901641 is about 270.9960511945.

The spelling of 19901641 in words is "nineteen million, nine hundred one thousand, six hundred forty-one".