21337891 has 2 divisors, whose sum is σ = 21337892. Its totient is φ = 21337890.

The previous prime is 21337867. The next prime is 21337913. The reversal of 21337891 is 19873312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21337891 - 2¹³ = 21329699 is a prime.

It is not a weakly prime, because it can be changed into another prime (21337801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10668945 + 10668946.

It is an arithmetic number, because the mean of its divisors is an integer number (10668946).

Almost surely, 2^21337891 is an apocalyptic number.

21337891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21337891 is an equidigital number, since it uses as much as digits as its factorization.

21337891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 21337891 is about 4619.2955090576. The cubic root of 21337891 is about 277.3642590187.

The spelling of 21337891 in words is "twenty-one million, three hundred thirty-seven thousand, eight hundred ninety-one".