21216497 has 2 divisors, whose sum is σ = 21216498. Its totient is φ = 21216496.

The previous prime is 21216479. The next prime is 21216529. The reversal of 21216497 is 79461212.

It is a happy number.

Together with previous prime (21216479) it forms an Ormiston pair, because they use the same digits, order apart.

It is an a-pointer prime, because the next prime (21216529) can be obtained adding 21216497 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14409616 + 6806881 = 3796^2 + 2609^2 .

It is a cyclic number.

It is not a de Polignac number, because 21216497 - 2⁸ = 21216241 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21216427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608248 + 10608249.

It is an arithmetic number, because the mean of its divisors is an integer number (10608249).

Almost surely, 2^21216497 is an apocalyptic number.

It is an amenable number.

21216497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216497 is an equidigital number, since it uses as much as digits as its factorization.

21216497 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 32.

The square root of 21216497 is about 4606.1368846355. The cubic root of 21216497 is about 276.8372714312.

The spelling of 21216497 in words is "twenty-one million, two hundred sixteen thousand, four hundred ninety-seven".