21551355 has 48 divisors (see below), whose sum is σ = 44089344. Its totient is φ = 9529920.

The previous prime is 21551351. The next prime is 21551357. The reversal of 21551355 is 55315512.

It is not a de Polignac number, because 21551355 - 2² = 21551351 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21551351) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 8662 + ... + 10868.

It is an arithmetic number, because the mean of its divisors is an integer number (918528).

Almost surely, 2^21551355 is an apocalyptic number.

21551355 is an abundant number, since it is smaller than the sum of its proper divisors (22537989).

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

21551355 is a wasteful number, since it uses less digits than its factorization.

21551355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2256 (or 2253 counting only the distinct ones).

The product of its digits is 3750, while the sum is 27.

The square root of 21551355 is about 4642.3436968842. The cubic root of 21551355 is about 278.2861079792.

Adding to 21551355 its reverse (55315512), we get a palindrome (76866867).

The spelling of 21551355 in words is "twenty-one million, five hundred fifty-one thousand, three hundred fifty-five".