20321621 has 16 divisors (see below), whose sum is σ = 22234560. Its totient is φ = 18506880.

The previous prime is 20321617. The next prime is 20321641. The reversal of 20321621 is 12612302.

It is a cyclic number.

It is not a de Polignac number, because 20321621 - 2² = 20321617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20321621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20321641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96206 + ... + 96416.

It is an arithmetic number, because the mean of its divisors is an integer number (1389660).

Almost surely, 2^20321621 is an apocalyptic number.

20321621 is the 2603-rd octagonal number.

It is an amenable number.

20321621 is a deficient number, since it is larger than the sum of its proper divisors (1912939).

20321621 is a wasteful number, since it uses less digits than its factorization.

20321621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 20321621 is about 4507.9508648609. The cubic root of 20321621 is about 272.8890540160.

Adding to 20321621 its reverse (12612302), we get a palindrome (32933923).

The spelling of 20321621 in words is "twenty million, three hundred twenty-one thousand, six hundred twenty-one".