21231640 has 32 divisors (see below), whose sum is σ = 50582880. Its totient is φ = 7992832.

The previous prime is 21231631. The next prime is 21231677. The reversal of 21231640 is 4613212.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 14932 + ... + 16291.

It is an arithmetic number, because the mean of its divisors is an integer number (1580715).

Almost surely, 2^21231640 is an apocalyptic number.

21231640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231640 is an abundant number, since it is smaller than the sum of its proper divisors (29351240).

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

21231640 is a wasteful number, since it uses less digits than its factorization.

21231640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31251 (or 31247 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21231640 is about 4607.7803767107. The cubic root of 21231640 is about 276.9031187737.

Adding to 21231640 its reverse (4613212), we get a palindrome (25844852).

The spelling of 21231640 in words is "twenty-one million, two hundred thirty-one thousand, six hundred forty".