21413891 has 2 divisors, whose sum is σ = 21413892. Its totient is φ = 21413890.

The previous prime is 21413881. The next prime is 21413939. The reversal of 21413891 is 19831412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21413891 - 2⁶ = 21413827 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21413881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10706945 + 10706946.

It is an arithmetic number, because the mean of its divisors is an integer number (10706946).

Almost surely, 2^21413891 is an apocalyptic number.

21413891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21413891 is an equidigital number, since it uses as much as digits as its factorization.

21413891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 21413891 is about 4627.5145596746. The cubic root of 21413891 is about 277.6931685364.

The spelling of 21413891 in words is "twenty-one million, four hundred thirteen thousand, eight hundred ninety-one".