21712169 has 2 divisors, whose sum is σ = 21712170. Its totient is φ = 21712168.

The previous prime is 21712153. The next prime is 21712211. The reversal of 21712169 is 96121712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 1236544 = 4525^2 + 1112^2 .

It is a cyclic number.

It is not a de Polignac number, because 21712169 - 2⁴ = 21712153 is a prime.

It is a super-2 number, since 2×21712169² = 942836565369122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21712109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10856084 + 10856085.

It is an arithmetic number, because the mean of its divisors is an integer number (10856085).

Almost surely, 2^21712169 is an apocalyptic number.

It is an amenable number.

21712169 is a deficient number, since it is larger than the sum of its proper divisors (1).

21712169 is an equidigital number, since it uses as much as digits as its factorization.

21712169 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 29.

The square root of 21712169 is about 4659.6318524107. The cubic root of 21712169 is about 278.9765742162.

It can be divided in two parts, 2 and 1712169, that added together give a palindrome (1712171).

The spelling of 21712169 in words is "twenty-one million, seven hundred twelve thousand, one hundred sixty-nine".