21395537 has 12 divisors (see below), whose sum is σ = 22984476. Its totient is φ = 19910400.

The previous prime is 21395527. The next prime is 21395551. The reversal of 21395537 is 73559312.

It is a happy number.

21395537 is nontrivially palindromic in base 8.

It can be written as a sum of positive squares in 6 ways, for example, as 13278736 + 8116801 = 3644^2 + 2849^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21395537 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21395497 and 21395506.

It is not an unprimeable number, because it can be changed into a prime (21395527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28823 + ... + 29555.

It is an arithmetic number, because the mean of its divisors is an integer number (1915373).

Almost surely, 2^21395537 is an apocalyptic number.

It is an amenable number.

21395537 is a deficient number, since it is larger than the sum of its proper divisors (1588939).

21395537 is a wasteful number, since it uses less digits than its factorization.

21395537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 868 (or 851 counting only the distinct ones).

The product of its digits is 28350, while the sum is 35.

The square root of 21395537 is about 4625.5309965452. The cubic root of 21395537 is about 277.6138082546.

The spelling of 21395537 in words is "twenty-one million, three hundred ninety-five thousand, five hundred thirty-seven".