21690129 has 4 divisors (see below), whose sum is σ = 28920176. Its totient is φ = 14460084.

The previous prime is 21690121. The next prime is 21690131. The reversal of 21690129 is 92109612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21690129 - 2³ = 21690121 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21690096 and 21690105.

It is not an unprimeable number, because it can be changed into a prime (21690121) 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 in 3 ways as a sum of consecutive naturals, for example, 3615019 + ... + 3615024.

It is an arithmetic number, because the mean of its divisors is an integer number (7230044).

Almost surely, 2^21690129 is an apocalyptic number.

It is an amenable number.

21690129 is a deficient number, since it is larger than the sum of its proper divisors (7230047).

21690129 is an equidigital number, since it uses as much as digits as its factorization.

21690129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7230046.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 21690129 is about 4657.2662582249. The cubic root of 21690129 is about 278.8821459816.

The spelling of 21690129 in words is "twenty-one million, six hundred ninety thousand, one hundred twenty-nine".