21378829 has 8 divisors (see below), whose sum is σ = 22448160. Its totient is φ = 20331696.

The previous prime is 21378817. The next prime is 21378883. The reversal of 21378829 is 92887312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21378829 - 2⁷ = 21378701 is a prime.

It is a super-2 number, since 2×21378829² = 914108658822482, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21378791 and 21378800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378899) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3559 + ... + 7444.

It is an arithmetic number, because the mean of its divisors is an integer number (2806020).

Almost surely, 2^21378829 is an apocalyptic number.

21378829 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21378829 is a deficient number, since it is larger than the sum of its proper divisors (1069331).

21378829 is a wasteful number, since it uses less digits than its factorization.

21378829 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11099.

The product of its digits is 48384, while the sum is 40.

The square root of 21378829 is about 4623.7245808980. The cubic root of 21378829 is about 277.5415255878.

The spelling of 21378829 in words is "twenty-one million, three hundred seventy-eight thousand, eight hundred twenty-nine".