18861421 has 2 divisors, whose sum is σ = 18861422. Its totient is φ = 18861420.

The previous prime is 18861407. The next prime is 18861439. The reversal of 18861421 is 12416881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17682025 + 1179396 = 4205^2 + 1086^2 .

It is a cyclic number.

It is not a de Polignac number, because 18861421 - 2¹⁹ = 18337133 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18861461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9430710 + 9430711.

It is an arithmetic number, because the mean of its divisors is an integer number (9430711).

Almost surely, 2^18861421 is an apocalyptic number.

It is an amenable number.

18861421 is a deficient number, since it is larger than the sum of its proper divisors (1).

18861421 is an equidigital number, since it uses as much as digits as its factorization.

18861421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3072, while the sum is 31.

The square root of 18861421 is about 4342.9737507841. The cubic root of 18861421 is about 266.1898365975.

The spelling of 18861421 in words is "eighteen million, eight hundred sixty-one thousand, four hundred twenty-one".