21390829 has 4 divisors (see below), whose sum is σ = 21486976. Its totient is φ = 21294684.

The previous prime is 21390797. The next prime is 21390833. The reversal of 21390829 is 92809312.

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 21390829 - 2⁵ = 21390797 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21390794 and 21390803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21394829) 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, 47739 + ... + 48184.

It is an arithmetic number, because the mean of its divisors is an integer number (5371744).

Almost surely, 2^21390829 is an apocalyptic number.

It is an amenable number.

21390829 is a deficient number, since it is larger than the sum of its proper divisors (96147).

21390829 is an equidigital number, since it uses as much as digits as its factorization.

21390829 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96146.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 21390829 is about 4625.0220540015. The cubic root of 21390829 is about 277.5934441683.

The spelling of 21390829 in words is "twenty-one million, three hundred ninety thousand, eight hundred twenty-nine".