21769831 has 2 divisors, whose sum is σ = 21769832. Its totient is φ = 21769830.

The previous prime is 21769829. The next prime is 21769837. The reversal of 21769831 is 13896712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21769831 - 2¹ = 21769829 is a prime.

It is a super-2 number, since 2×21769831² = 947851083537122, which contains 22 as substring.

Together with 21769829, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21769837) 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, 10884915 + 10884916.

It is an arithmetic number, because the mean of its divisors is an integer number (10884916).

Almost surely, 2^21769831 is an apocalyptic number.

21769831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21769831 is an equidigital number, since it uses as much as digits as its factorization.

21769831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 37.

The square root of 21769831 is about 4665.8151485030. The cubic root of 21769831 is about 279.2233195288.

The spelling of 21769831 in words is "twenty-one million, seven hundred sixty-nine thousand, eight hundred thirty-one".