21645629 has 8 divisors (see below), whose sum is σ = 22998360. Its totient is φ = 20333376.

The previous prime is 21645619. The next prime is 21645683. The reversal of 21645629 is 92654612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 15405625 + 6240004 = 3925^2 + 2498^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21645629 - 2⁸ = 21645373 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 (21645619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9014 + ... + 11159.

It is an arithmetic number, because the mean of its divisors is an integer number (2874795).

Almost surely, 2^21645629 is an apocalyptic number.

21645629 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21645629 is a deficient number, since it is larger than the sum of its proper divisors (1352731).

21645629 is a wasteful number, since it uses less digits than its factorization.

21645629 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20239.

The product of its digits is 25920, while the sum is 35.

The square root of 21645629 is about 4652.4863245366. The cubic root of 21645629 is about 278.6912949230.

The spelling of 21645629 in words is "twenty-one million, six hundred forty-five thousand, six hundred twenty-nine".