21047537 has 4 divisors (see below), whose sum is σ = 24054336. Its totient is φ = 18040740.

The previous prime is 21047531. The next prime is 21047539. The reversal of 21047537 is 73574012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21047537 - 2⁸ = 21047281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21047531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1503389 + ... + 1503402.

It is an arithmetic number, because the mean of its divisors is an integer number (6013584).

Almost surely, 2^21047537 is an apocalyptic number.

It is an amenable number.

21047537 is a deficient number, since it is larger than the sum of its proper divisors (3006799).

21047537 is an equidigital number, since it uses as much as digits as its factorization.

21047537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3006798.

The product of its (nonzero) digits is 5880, while the sum is 29.

The square root of 21047537 is about 4587.7594749507. The cubic root of 21047537 is about 276.1004369113.

The spelling of 21047537 in words is "twenty-one million, forty-seven thousand, five hundred thirty-seven".