21322640 has 40 divisors (see below), whose sum is σ = 49868088. Its totient is φ = 8478720.

The previous prime is 21322621. The next prime is 21322661. The reversal of 21322640 is 4622312.

It can be written as a sum of positive squares in 4 ways, for example, as 565504 + 20757136 = 752^2 + 4556^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-3 number, since 3×21322640³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

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, 14750 + ... + 16130.

Almost surely, 2^21322640 is an apocalyptic number.

21322640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21322640 is an abundant number, since it is smaller than the sum of its proper divisors (28545448).

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

21322640 is a wasteful number, since it uses less digits than its factorization.

21322640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1587 (or 1581 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21322640 is about 4617.6444211308. The cubic root of 21322640 is about 277.2981623503.

Adding to 21322640 its reverse (4622312), we get a palindrome (25944952).

The spelling of 21322640 in words is "twenty-one million, three hundred twenty-two thousand, six hundred forty".