21690829 has 4 divisors (see below), whose sum is σ = 22152384. Its totient is φ = 21229276.

The previous prime is 21690821. The next prime is 21690853. The reversal of 21690829 is 92809612.

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 a cyclic number.

It is not a de Polignac number, because 21690829 - 2³ = 21690821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 230707 + ... + 230800.

It is an arithmetic number, because the mean of its divisors is an integer number (5538096).

Almost surely, 2^21690829 is an apocalyptic number.

It is an amenable number.

21690829 is a deficient number, since it is larger than the sum of its proper divisors (461555).

21690829 is an equidigital number, since it uses as much as digits as its factorization.

21690829 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 461554.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 21690829 is about 4657.3414090015. The cubic root of 21690829 is about 278.8851460468.

The spelling of 21690829 in words is "twenty-one million, six hundred ninety thousand, eight hundred twenty-nine".