21629569 has 4 divisors (see below), whose sum is σ = 23293396. Its totient is φ = 19965744.

The previous prime is 21629561. The next prime is 21629579. The reversal of 21629569 is 96592612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10660225 + 10969344 = 3265^2 + 3312^2 .

It is a cyclic number.

It is not a de Polignac number, because 21629569 - 2³ = 21629561 is a prime.

It is a super-2 number, since 2×21629569² = 935676510251522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21629561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 831894 + ... + 831919.

It is an arithmetic number, because the mean of its divisors is an integer number (5823349).

Almost surely, 2^21629569 is an apocalyptic number.

It is an amenable number.

21629569 is a deficient number, since it is larger than the sum of its proper divisors (1663827).

21629569 is a wasteful number, since it uses less digits than its factorization.

21629569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1663826.

The product of its digits is 58320, while the sum is 40.

The square root of 21629569 is about 4650.7600454119. The cubic root of 21629569 is about 278.6223527578.

The spelling of 21629569 in words is "twenty-one million, six hundred twenty-nine thousand, five hundred sixty-nine".