21378942 has 48 divisors (see below), whose sum is σ = 50236368. Its totient is φ = 6531840.

The previous prime is 21378923. The next prime is 21378949. The reversal of 21378942 is 24987312.

It is a super-2 number, since 2×21378942² = 914118322078728, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21378897 and 21378906.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378949) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49158 + ... + 49590.

It is an arithmetic number, because the mean of its divisors is an integer number (1046591).

Almost surely, 2^21378942 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21378942, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25118184).

21378942 is an abundant number, since it is smaller than the sum of its proper divisors (28857426).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21378942 is a wasteful number, since it uses less digits than its factorization.

21378942 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 665 (or 662 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21378942 is about 4623.7368004678. The cubic root of 21378942 is about 277.5420145784.

The spelling of 21378942 in words is "twenty-one million, three hundred seventy-eight thousand, nine hundred forty-two".