21553340 has 24 divisors (see below), whose sum is σ = 45593520. Its totient is φ = 8558208.

The previous prime is 21553319. The next prime is 21553361. The reversal of 21553340 is 4335512.

It is an interprime number because it is at equal distance from previous prime (21553319) and next prime (21553361).

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, 1097 + ... + 6656.

It is an arithmetic number, because the mean of its divisors is an integer number (1899730).

Almost surely, 2^21553340 is an apocalyptic number.

21553340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21553340 is an abundant number, since it is smaller than the sum of its proper divisors (24040180).

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

21553340 is a wasteful number, since it uses less digits than its factorization.

21553340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7901 (or 7899 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 23.

The square root of 21553340 is about 4642.5574848353. The cubic root of 21553340 is about 278.2946516178.

Adding to 21553340 its reverse (4335512), we get a palindrome (25888852).

The spelling of 21553340 in words is "twenty-one million, five hundred fifty-three thousand, three hundred forty".