21220737 has 4 divisors (see below), whose sum is σ = 28294320. Its totient is φ = 14147156.

The previous prime is 21220733. The next prime is 21220751. The reversal of 21220737 is 73702212.

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 21220737 - 2² = 21220733 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21220733) 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, 3536787 + ... + 3536792.

It is an arithmetic number, because the mean of its divisors is an integer number (7073580).

Almost surely, 2^21220737 is an apocalyptic number.

It is an amenable number.

21220737 is a deficient number, since it is larger than the sum of its proper divisors (7073583).

21220737 is an equidigital number, since it uses as much as digits as its factorization.

21220737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7073582.

The product of its (nonzero) digits is 1176, while the sum is 24.

The square root of 21220737 is about 4606.5971171788. The cubic root of 21220737 is about 276.8557116706.

Adding to 21220737 its reverse (73702212), we get a palindrome (94922949).

The spelling of 21220737 in words is "twenty-one million, two hundred twenty thousand, seven hundred thirty-seven".