21131340 has 48 divisors (see below), whose sum is σ = 62651232. Its totient is φ = 5303296.

The previous prime is 21131333. The next prime is 21131389. The reversal of 21131340 is 4313112.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9339 + ... + 11378.

It is an arithmetic number, because the mean of its divisors is an integer number (1305234).

Almost surely, 2^21131340 is an apocalyptic number.

21131340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21131340 is an abundant number, since it is smaller than the sum of its proper divisors (41519892).

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

21131340 is a wasteful number, since it uses less digits than its factorization.

21131340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20746 (or 20744 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21131340 is about 4596.8837270481. The cubic root of 21131340 is about 276.4663926968.

Adding to 21131340 its reverse (4313112), we get a palindrome (25444452).

The spelling of 21131340 in words is "twenty-one million, one hundred thirty-one thousand, three hundred forty".