21421019509 has 2 divisors, whose sum is σ = 21421019510. Its totient is φ = 21421019508.

The previous prime is 21421019461. The next prime is 21421019519. The reversal of 21421019509 is 90591012412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10739176900 + 10681842609 = 103630^2 + 103353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21421019509 - 2¹⁹ = 21420495221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21421019519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710509754 + 10710509755.

It is an arithmetic number, because the mean of its divisors is an integer number (10710509755).

Almost surely, 2^21421019509 is an apocalyptic number.

It is an amenable number.

21421019509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21421019509 is an equidigital number, since it uses as much as digits as its factorization.

21421019509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 34.

The spelling of 21421019509 in words is "twenty-one billion, four hundred twenty-one million, nineteen thousand, five hundred nine".