21161637 has 24 divisors (see below), whose sum is σ = 35096256. Its totient is φ = 12036096.

The previous prime is 21161627. The next prime is 21161639. The reversal of 21161637 is 73616112.

21161637 is a `hidden beast` number, since 2 + 11 + 616 + 37 = 666.

It is not a de Polignac number, because 21161637 - 2⁷ = 21161509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21161637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21161639) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15538 + ... + 16844.

It is an arithmetic number, because the mean of its divisors is an integer number (1462344).

Almost surely, 2^21161637 is an apocalyptic number.

It is an amenable number.

21161637 is a deficient number, since it is larger than the sum of its proper divisors (13934619).

21161637 is a wasteful number, since it uses less digits than its factorization.

21161637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1577 (or 1574 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21161637 is about 4600.1779313414. The cubic root of 21161637 is about 276.5984572419.

Adding to 21161637 its reverse (73616112), we get a palindrome (94777749).

The spelling of 21161637 in words is "twenty-one million, one hundred sixty-one thousand, six hundred thirty-seven".