21986197 has 2 divisors, whose sum is σ = 21986198. Its totient is φ = 21986196.

The previous prime is 21986191. The next prime is 21986203. The reversal of 21986197 is 79168912.

It is a balanced prime because it is at equal distance from previous prime (21986191) and next prime (21986203).

It can be written as a sum of positive squares in only one way, i.e., 21150801 + 835396 = 4599^2 + 914^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21986197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21986191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10993098 + 10993099.

It is an arithmetic number, because the mean of its divisors is an integer number (10993099).

Almost surely, 2^21986197 is an apocalyptic number.

It is an amenable number.

21986197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21986197 is an equidigital number, since it uses as much as digits as its factorization.

21986197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 43.

The square root of 21986197 is about 4688.9441242139. The cubic root of 21986197 is about 280.1453199741.

The spelling of 21986197 in words is "twenty-one million, nine hundred eighty-six thousand, one hundred ninety-seven".