21515442901 has 4 divisors (see below), whose sum is σ = 21670230400. Its totient is φ = 21360655404.

The previous prime is 21515442863. The next prime is 21515442917. The reversal of 21515442901 is 10924451512.

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 21515442901 - 2¹¹ = 21515440853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515442931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77393541 + ... + 77393818.

It is an arithmetic number, because the mean of its divisors is an integer number (5417557600).

Almost surely, 2^21515442901 is an apocalyptic number.

It is an amenable number.

21515442901 is a deficient number, since it is larger than the sum of its proper divisors (154787499).

21515442901 is a wasteful number, since it uses less digits than its factorization.

21515442901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154787498.

The product of its (nonzero) digits is 14400, while the sum is 34.

The spelling of 21515442901 in words is "twenty-one billion, five hundred fifteen million, four hundred forty-two thousand, nine hundred one".