16920401021 has 2 divisors, whose sum is σ = 16920401022. Its totient is φ = 16920401020.

The previous prime is 16920401009. The next prime is 16920401027. The reversal of 16920401021 is 12010402961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16519960900 + 400440121 = 128530^2 + 20011^2 .

It is a cyclic number.

It is not a de Polignac number, because 16920401021 - 2¹⁰ = 16920399997 is a prime.

It is a super-2 number, since 2×16920401021² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16920401027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8460200510 + 8460200511.

It is an arithmetic number, because the mean of its divisors is an integer number (8460200511).

Almost surely, 2^16920401021 is an apocalyptic number.

It is an amenable number.

16920401021 is a deficient number, since it is larger than the sum of its proper divisors (1).

16920401021 is an equidigital number, since it uses as much as digits as its factorization.

16920401021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 26.

Adding to 16920401021 its reverse (12010402961), we get a palindrome (28930803982).

The spelling of 16920401021 in words is "sixteen billion, nine hundred twenty million, four hundred one thousand, twenty-one".