1891551421 has 2 divisors, whose sum is σ = 1891551422. Its totient is φ = 1891551420.

The previous prime is 1891551383. The next prime is 1891551499. The reversal of 1891551421 is 1241551981.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1240025796 + 651525625 = 35214^2 + 25525^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1891551421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1891251421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 945775710 + 945775711.

It is an arithmetic number, because the mean of its divisors is an integer number (945775711).

Almost surely, 2^1891551421 is an apocalyptic number.

It is an amenable number.

1891551421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1891551421 is an equidigital number, since it uses as much as digits as its factorization.

1891551421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14400, while the sum is 37.

The square root of 1891551421 is about 43491.9696150910. The cubic root of 1891551421 is about 1236.7237962854.

The spelling of 1891551421 in words is "one billion, eight hundred ninety-one million, five hundred fifty-one thousand, four hundred twenty-one".