21397711 has 2 divisors, whose sum is σ = 21397712. Its totient is φ = 21397710.

The previous prime is 21397699. The next prime is 21397769. The reversal of 21397711 is 11779312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21397711 - 2¹¹ = 21395663 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21397771) 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, 10698855 + 10698856.

It is an arithmetic number, because the mean of its divisors is an integer number (10698856).

Almost surely, 2^21397711 is an apocalyptic number.

21397711 is a deficient number, since it is larger than the sum of its proper divisors (1).

21397711 is an equidigital number, since it uses as much as digits as its factorization.

21397711 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2646, while the sum is 31.

The square root of 21397711 is about 4625.7659906225. The cubic root of 21397711 is about 277.6232107136.

The spelling of 21397711 in words is "twenty-one million, three hundred ninety-seven thousand, seven hundred eleven".