21620217 has 4 divisors (see below), whose sum is σ = 28826960. Its totient is φ = 14413476.

The previous prime is 21620197. The next prime is 21620227. The reversal of 21620217 is 71202612.

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 not a de Polignac number, because 21620217 - 2⁶ = 21620153 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21620193 and 21620202.

It is not an unprimeable number, because it can be changed into a prime (21620227) 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, 3603367 + ... + 3603372.

It is an arithmetic number, because the mean of its divisors is an integer number (7206740).

Almost surely, 2^21620217 is an apocalyptic number.

It is an amenable number.

21620217 is a deficient number, since it is larger than the sum of its proper divisors (7206743).

21620217 is an equidigital number, since it uses as much as digits as its factorization.

21620217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7206742.

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 21620217 is about 4649.7545096489. The cubic root of 21620217 is about 278.5821908869.

Adding to 21620217 its reverse (71202612), we get a palindrome (92822829).

The spelling of 21620217 in words is "twenty-one million, six hundred twenty thousand, two hundred seventeen".