21199897 has 2 divisors, whose sum is σ = 21199898. Its totient is φ = 21199896.

The previous prime is 21199891. The next prime is 21199909. The reversal of 21199897 is 79899112.

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., 12503296 + 8696601 = 3536^2 + 2949^2 .

It is a cyclic number.

It is not a de Polignac number, because 21199897 - 2²³ = 12811289 is a prime.

It is not a weakly prime, because it can be changed into another prime (21199891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10599948 + 10599949.

It is an arithmetic number, because the mean of its divisors is an integer number (10599949).

Almost surely, 2^21199897 is an apocalyptic number.

It is an amenable number.

21199897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21199897 is an equidigital number, since it uses as much as digits as its factorization.

21199897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81648, while the sum is 46.

The square root of 21199897 is about 4604.3345881897. The cubic root of 21199897 is about 276.7650525073.

The spelling of 21199897 in words is "twenty-one million, one hundred ninety-nine thousand, eight hundred ninety-seven".