221660537 has 4 divisors (see below), whose sum is σ = 253326336. Its totient is φ = 189994740.

The previous prime is 221660513. The next prime is 221660539. The reversal of 221660537 is 735066122.

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 221660537 - 2⁸ = 221660281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221660539) 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, 15832889 + ... + 15832902.

It is an arithmetic number, because the mean of its divisors is an integer number (63331584).

Almost surely, 2^221660537 is an apocalyptic number.

It is an amenable number.

221660537 is a deficient number, since it is larger than the sum of its proper divisors (31665799).

221660537 is an equidigital number, since it uses as much as digits as its factorization.

221660537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31665798.

The product of its (nonzero) digits is 15120, while the sum is 32.

The square root of 221660537 is about 14888.2684352479. The cubic root of 221660537 is about 605.1961088177.

The spelling of 221660537 in words is "two hundred twenty-one million, six hundred sixty thousand, five hundred thirty-seven".