21997487 has 2 divisors, whose sum is σ = 21997488. Its totient is φ = 21997486.

The previous prime is 21997477. The next prime is 21997513. The reversal of 21997487 is 78479912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21997487 - 2²² = 17803183 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21997447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10998743 + 10998744.

It is an arithmetic number, because the mean of its divisors is an integer number (10998744).

Almost surely, 2^21997487 is an apocalyptic number.

21997487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21997487 is an equidigital number, since it uses as much as digits as its factorization.

21997487 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 254016, while the sum is 47.

The square root of 21997487 is about 4690.1478654729. The cubic root of 21997487 is about 280.1932636823.

The spelling of 21997487 in words is "twenty-one million, nine hundred ninety-seven thousand, four hundred eighty-seven".