21865740 has 144 divisors (see below), whose sum is σ = 70762272. Its totient is φ = 5013504.

The previous prime is 21865721. The next prime is 21865741. The reversal of 21865740 is 4756812.

It is a super-2 number, since 2×21865740² = 956221171495200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21865741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 225372 + ... + 225468.

Almost surely, 2^21865740 is an apocalyptic number.

21865740 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 21865740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35381136).

21865740 is an abundant number, since it is smaller than the sum of its proper divisors (48896532).

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

21865740 is a wasteful number, since it uses less digits than its factorization.

21865740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156 (or 137 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21865740 is about 4676.0816930417. The cubic root of 21865740 is about 279.6327668664.

The spelling of 21865740 in words is "twenty-one million, eight hundred sixty-five thousand, seven hundred forty".