28737221 has 4 divisors (see below), whose sum is σ = 28846752. Its totient is φ = 28627692.

The previous prime is 28737211. The next prime is 28737223. The reversal of 28737221 is 12273782.

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 a de Polignac number, because none of the positive numbers 2^k-28737221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28737223) 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, 54371 + ... + 54896.

It is an arithmetic number, because the mean of its divisors is an integer number (7211688).

Almost surely, 2^28737221 is an apocalyptic number.

It is an amenable number.

28737221 is a deficient number, since it is larger than the sum of its proper divisors (109531).

28737221 is a wasteful number, since it uses less digits than its factorization.

28737221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109530.

The product of its digits is 9408, while the sum is 32.

The square root of 28737221 is about 5360.7108670399. The cubic root of 28737221 is about 306.3008880591.

The spelling of 28737221 in words is "twenty-eight million, seven hundred thirty-seven thousand, two hundred twenty-one".