21629389 has 16 divisors (see below), whose sum is σ = 24055920. Its totient is φ = 19353600.

The previous prime is 21629381. The next prime is 21629393. The reversal of 21629389 is 98392612.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 2992900 + 18636489 = 1730^2 + 4317^2 .

It is a cyclic number.

It is not a de Polignac number, because 21629389 - 2³ = 21629381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21629381) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 35689 + ... + 36289.

It is an arithmetic number, because the mean of its divisors is an integer number (1503495).

Almost surely, 2^21629389 is an apocalyptic number.

21629389 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21629389 is a deficient number, since it is larger than the sum of its proper divisors (2426531).

21629389 is a wasteful number, since it uses less digits than its factorization.

21629389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 720.

The product of its digits is 46656, while the sum is 40.

The square root of 21629389 is about 4650.7406936960. The cubic root of 21629389 is about 278.6215798627.

The spelling of 21629389 in words is "twenty-one million, six hundred twenty-nine thousand, three hundred eighty-nine".