21293940 has 48 divisors (see below), whose sum is σ = 60524352. Its totient is φ = 5592576.

The previous prime is 21293939. The next prime is 21293947. The reversal of 21293940 is 4939212.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21293898 and 21293907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21293947) 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 15 ways as a sum of consecutive naturals, for example, 1372 + ... + 6668.

It is an arithmetic number, because the mean of its divisors is an integer number (1260924).

Almost surely, 2^21293940 is an apocalyptic number.

21293940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21293940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30262176).

21293940 is an abundant number, since it is smaller than the sum of its proper divisors (39230412).

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

21293940 is a wasteful number, since it uses less digits than its factorization.

21293940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5376 (or 5374 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21293940 is about 4614.5357296265. The cubic root of 21293940 is about 277.1736932322.

The spelling of 21293940 in words is "twenty-one million, two hundred ninety-three thousand, nine hundred forty".