21609767 has 2 divisors, whose sum is σ = 21609768. Its totient is φ = 21609766.

The previous prime is 21609733. The next prime is 21609769. The reversal of 21609767 is 76790612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21609767 - 2¹⁶ = 21544231 is a prime.

Together with 21609769, 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 21609767.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21609769) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804883 + 10804884.

It is an arithmetic number, because the mean of its divisors is an integer number (10804884).

Almost surely, 2^21609767 is an apocalyptic number.

21609767 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609767 is an equidigital number, since it uses as much as digits as its factorization.

21609767 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31752, while the sum is 38.

The square root of 21609767 is about 4648.6306585918. The cubic root of 21609767 is about 278.5372999860.

The spelling of 21609767 in words is "twenty-one million, six hundred nine thousand, seven hundred sixty-seven".