21629745 has 12 divisors (see below), whose sum is σ = 37491636. Its totient is φ = 11535840.

The previous prime is 21629743. The next prime is 21629747. The reversal of 21629745 is 54792612.

21629745 is a `hidden beast` number, since 21 + 629 + 7 + 4 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (21629743) and next prime (21629747).

It can be written as a sum of positive squares in 2 ways, for example, as 13660416 + 7969329 = 3696^2 + 2823^2 .

It is not a de Polignac number, because 21629745 - 2¹ = 21629743 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21629743) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240286 + ... + 240375.

It is an arithmetic number, because the mean of its divisors is an integer number (3124303).

Almost surely, 2^21629745 is an apocalyptic number.

It is an amenable number.

21629745 is a deficient number, since it is larger than the sum of its proper divisors (15861891).

21629745 is a wasteful number, since it uses less digits than its factorization.

21629745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480672 (or 480669 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The square root of 21629745 is about 4650.7789670119. The cubic root of 21629745 is about 278.6231084733.

The spelling of 21629745 in words is "twenty-one million, six hundred twenty-nine thousand, seven hundred forty-five".