21020634 has 20 divisors (see below), whose sum is σ = 47102154. Its totient is φ = 7006824.

The previous prime is 21020633. The next prime is 21020641. The reversal of 21020634 is 43602012.

It is a happy number.

21020634 is a `hidden beast` number, since 2 + 10 + 20 + 634 = 666.

It can be written as a sum of positive squares in only one way, i.e., 20657025 + 363609 = 4545^2 + 603^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21020633) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 64717 + ... + 65040.

Almost surely, 2^21020634 is an apocalyptic number.

21020634 is an abundant number, since it is smaller than the sum of its proper divisors (26081520).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21020634 is a wasteful number, since it uses less digits than its factorization.

21020634 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129771 (or 129762 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21020634 is about 4584.8264961719. The cubic root of 21020634 is about 275.9827493944.

Adding to 21020634 its reverse (43602012), we get a palindrome (64622646).

The spelling of 21020634 in words is "twenty-one million, twenty thousand, six hundred thirty-four".