21525037 has 4 divisors (see below), whose sum is σ = 21543676. Its totient is φ = 21506400.

The previous prime is 21525017. The next prime is 21525059. The reversal of 21525037 is 73052512.

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 14523721 + 7001316 = 3811^2 + 2646^2 .

It is a cyclic number.

It is not a de Polignac number, because 21525037 - 2¹¹ = 21522989 is a prime.

It is a super-3 number, since 3×21525037³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21525017) 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 3 ways as a sum of consecutive naturals, for example, 7464 + ... + 9937.

It is an arithmetic number, because the mean of its divisors is an integer number (5385919).

Almost surely, 2^21525037 is an apocalyptic number.

It is an amenable number.

21525037 is a deficient number, since it is larger than the sum of its proper divisors (18639).

21525037 is a wasteful number, since it uses less digits than its factorization.

21525037 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18638.

The product of its (nonzero) digits is 2100, while the sum is 25.

The square root of 21525037 is about 4639.5082713581. The cubic root of 21525037 is about 278.1727830539.

Adding to 21525037 its reverse (73052512), we get a palindrome (94577549).

It can be divided in two parts, 215 and 25037, that added together give a palindrome (25252).

The spelling of 21525037 in words is "twenty-one million, five hundred twenty-five thousand, thirty-seven".