21185940 has 24 divisors (see below), whose sum is σ = 59320800. Its totient is φ = 5649568.

The previous prime is 21185939. The next prime is 21185947. The reversal of 21185940 is 4958112.

It is a happy number.

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 = 21185898 and 21185907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21185947) 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, 176490 + ... + 176609.

It is an arithmetic number, because the mean of its divisors is an integer number (2471700).

Almost surely, 2^21185940 is an apocalyptic number.

21185940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21185940 is an abundant number, since it is smaller than the sum of its proper divisors (38134860).

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

21185940 is a wasteful number, since it uses less digits than its factorization.

21185940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353111 (or 353109 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 30.

The square root of 21185940 is about 4602.8187016219. The cubic root of 21185940 is about 276.7043028750.

The spelling of 21185940 in words is "twenty-one million, one hundred eighty-five thousand, nine hundred forty".