21631155 has 96 divisors (see below), whose sum is σ = 45536256. Its totient is φ = 8566272.

The previous prime is 21631121. The next prime is 21631171. The reversal of 21631155 is 55113612.

It is not a de Polignac number, because 21631155 - 2⁸ = 21630899 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 408109 + ... + 408161.

It is an arithmetic number, because the mean of its divisors is an integer number (474336).

Almost surely, 2^21631155 is an apocalyptic number.

21631155 is an abundant number, since it is smaller than the sum of its proper divisors (23905101).

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

21631155 is a wasteful number, since it uses less digits than its factorization.

21631155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117 (or 104 counting only the distinct ones).

The product of its digits is 900, while the sum is 24.

The square root of 21631155 is about 4650.9305520508. The cubic root of 21631155 is about 278.6291626369.

Adding to 21631155 its reverse (55113612), we get a palindrome (76744767).

The spelling of 21631155 in words is "twenty-one million, six hundred thirty-one thousand, one hundred fifty-five".