21537537 has 16 divisors (see below), whose sum is σ = 33377280. Its totient is φ = 12097872.

The previous prime is 21537497. The next prime is 21537541. The reversal of 21537537 is 73573512.

It is not a de Polignac number, because 21537537 - 2⁶ = 21537473 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21537498 and 21537507.

It is not an unprimeable number, because it can be changed into a prime (21537547) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7453 + ... + 9930.

It is an arithmetic number, because the mean of its divisors is an integer number (2086080).

Almost surely, 2^21537537 is an apocalyptic number.

It is an amenable number.

21537537 is a deficient number, since it is larger than the sum of its proper divisors (11839743).

21537537 is a wasteful number, since it uses less digits than its factorization.

21537537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17452.

The product of its digits is 22050, while the sum is 33.

The square root of 21537537 is about 4640.8552013611. The cubic root of 21537537 is about 278.2266193829.

The spelling of 21537537 in words is "twenty-one million, five hundred thirty-seven thousand, five hundred thirty-seven".