21235997 has 2 divisors, whose sum is σ = 21235998. Its totient is φ = 21235996.

The previous prime is 21235993. The next prime is 21235999. The reversal of 21235997 is 79953212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17131321 + 4104676 = 4139^2 + 2026^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235997 - 2² = 21235993 is a prime.

Together with 21235999, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21235997.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21235993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617998 + 10617999.

It is an arithmetic number, because the mean of its divisors is an integer number (10617999).

Almost surely, 2^21235997 is an apocalyptic number.

It is an amenable number.

21235997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21235997 is an equidigital number, since it uses as much as digits as its factorization.

21235997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34020, while the sum is 38.

The square root of 21235997 is about 4608.2531397483. The cubic root of 21235997 is about 276.9220588143.

The spelling of 21235997 in words is "twenty-one million, two hundred thirty-five thousand, nine hundred ninety-seven".