21169381 has 2 divisors, whose sum is σ = 21169382. Its totient is φ = 21169380.

The previous prime is 21169367. The next prime is 21169397. The reversal of 21169381 is 18396112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11621281 + 9548100 = 3409^2 + 3090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21169381 - 2¹⁵ = 21136613 is a prime.

It is a super-2 number, since 2×21169381² = 896285383846322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21169321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10584690 + 10584691.

It is an arithmetic number, because the mean of its divisors is an integer number (10584691).

Almost surely, 2^21169381 is an apocalyptic number.

It is an amenable number.

21169381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21169381 is an equidigital number, since it uses as much as digits as its factorization.

21169381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 31.

The square root of 21169381 is about 4601.0195609234. The cubic root of 21169381 is about 276.6321930886.

The spelling of 21169381 in words is "twenty-one million, one hundred sixty-nine thousand, three hundred eighty-one".