21861767 has 2 divisors, whose sum is σ = 21861768. Its totient is φ = 21861766.

The previous prime is 21861757. The next prime is 21861769. The reversal of 21861767 is 76716812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21861767 - 2¹⁸ = 21599623 is a prime.

Together with 21861769, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21861767.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21861769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10930883 + 10930884.

It is an arithmetic number, because the mean of its divisors is an integer number (10930884).

Almost surely, 2^21861767 is an apocalyptic number.

21861767 is a deficient number, since it is larger than the sum of its proper divisors (1).

21861767 is an equidigital number, since it uses as much as digits as its factorization.

21861767 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 28224, while the sum is 38.

The square root of 21861767 is about 4675.6568522508. The cubic root of 21861767 is about 279.6158294371.

The spelling of 21861767 in words is "twenty-one million, eight hundred sixty-one thousand, seven hundred sixty-seven".