21215497 has 2 divisors, whose sum is σ = 21215498. Its totient is φ = 21215496.

The previous prime is 21215489. The next prime is 21215503. The reversal of 21215497 is 79451212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12595401 + 8620096 = 3549^2 + 2936^2 .

It is a cyclic number.

It is not a de Polignac number, because 21215497 - 2³ = 21215489 is a prime.

It is not a weakly prime, because it can be changed into another prime (21215437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607748 + 10607749.

It is an arithmetic number, because the mean of its divisors is an integer number (10607749).

Almost surely, 2^21215497 is an apocalyptic number.

It is an amenable number.

21215497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215497 is an equidigital number, since it uses as much as digits as its factorization.

21215497 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5040, while the sum is 31.

The square root of 21215497 is about 4606.0283325225. The cubic root of 21215497 is about 276.8329219601.

It can be divided in two parts, 21215 and 497, that added together give a palindrome (21712).

The spelling of 21215497 in words is "twenty-one million, two hundred fifteen thousand, four hundred ninety-seven".