21631129 has 16 divisors (see below), whose sum is σ = 24307920. Its totient is φ = 19111680.

The previous prime is 21631121. The next prime is 21631171. The reversal of 21631129 is 92113612.

It can be written as a sum of positive squares in 8 ways, for example, as 11055625 + 10575504 = 3325^2 + 3252^2 .

It is a cyclic number.

It is not a de Polignac number, because 21631129 - 2³ = 21631121 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21631121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 68079 + ... + 68395.

It is an arithmetic number, because the mean of its divisors is an integer number (1519245).

Almost surely, 2^21631129 is an apocalyptic number.

21631129 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21631129 is a deficient number, since it is larger than the sum of its proper divisors (2676791).

21631129 is a wasteful number, since it uses less digits than its factorization.

21631129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 540.

The product of its digits is 648, while the sum is 25.

The square root of 21631129 is about 4650.9277569104. The cubic root of 21631129 is about 278.6290510023.

The spelling of 21631129 in words is "twenty-one million, six hundred thirty-one thousand, one hundred twenty-nine".