21001515389 has 2 divisors, whose sum is σ = 21001515390. Its totient is φ = 21001515388.

The previous prime is 21001515383. The next prime is 21001515407. The reversal of 21001515389 is 98351510012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17212128025 + 3789387364 = 131195^2 + 61558^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001515389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001515383) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500757694 + 10500757695.

It is an arithmetic number, because the mean of its divisors is an integer number (10500757695).

Almost surely, 2^21001515389 is an apocalyptic number.

It is an amenable number.

21001515389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001515389 is an equidigital number, since it uses as much as digits as its factorization.

21001515389 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10800, while the sum is 35.

The spelling of 21001515389 in words is "twenty-one billion, one million, five hundred fifteen thousand, three hundred eighty-nine".