21840412 has 24 divisors (see below), whose sum is σ = 42094080. Its totient is φ = 9832560.

The previous prime is 21840407. The next prime is 21840421. The reversal of 21840412 is 21404812.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2389 + ... + 7027.

It is an arithmetic number, because the mean of its divisors is an integer number (1753920).

Almost surely, 2^21840412 is an apocalyptic number.

21840412 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21840412 is a deficient number, since it is larger than the sum of its proper divisors (20253668).

21840412 is a wasteful number, since it uses less digits than its factorization.

21840412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4761 (or 4759 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 22.

The square root of 21840412 is about 4673.3726579420. The cubic root of 21840412 is about 279.5247550460.

Subtracting from 21840412 its reverse (21404812), we obtain a square (435600 = 660²).

The spelling of 21840412 in words is "twenty-one million, eight hundred forty thousand, four hundred twelve".