21820169 has 16 divisors (see below), whose sum is σ = 26164992. Its totient is φ = 17791488.

The previous prime is 21820157. The next prime is 21820171. The reversal of 21820169 is 96102812.

It is a cyclic number.

It is not a de Polignac number, because 21820169 - 2¹⁶ = 21754633 is a prime.

It is a super-2 number, since 2×21820169² = 952239550377122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21820069) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50177 + ... + 50609.

It is an arithmetic number, because the mean of its divisors is an integer number (1635312).

Almost surely, 2^21820169 is an apocalyptic number.

It is an amenable number.

21820169 is a deficient number, since it is larger than the sum of its proper divisors (4344823).

21820169 is a wasteful number, since it uses less digits than its factorization.

21820169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 776.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21820169 is about 4671.2063752311. The cubic root of 21820169 is about 279.4383682644.

The spelling of 21820169 in words is "twenty-one million, eight hundred twenty thousand, one hundred sixty-nine".