21019812481 has 4 divisors (see below), whose sum is σ = 21026073600. Its totient is φ = 21013551364.

The previous prime is 21019812479. The next prime is 21019812497. The reversal of 21019812481 is 18421891012.

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 21019812481 - 2¹ = 21019812479 is a prime.

It is a super-2 number, since 2×21019812481² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21019812481.

It is not an unprimeable number, because it can be changed into a prime (21019812581) 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, 3125521 + ... + 3132238.

It is an arithmetic number, because the mean of its divisors is an integer number (5256518400).

Almost surely, 2^21019812481 is an apocalyptic number.

It is an amenable number.

21019812481 is a deficient number, since it is larger than the sum of its proper divisors (6261119).

21019812481 is an equidigital number, since it uses as much as digits as its factorization.

21019812481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6261118.

The product of its (nonzero) digits is 9216, while the sum is 37.

The spelling of 21019812481 in words is "twenty-one billion, nineteen million, eight hundred twelve thousand, four hundred eighty-one".