21001545505 has 16 divisors (see below), whose sum is σ = 26016186240. Its totient is φ = 16265265408.

The previous prime is 21001545503. The next prime is 21001545511. The reversal of 21001545505 is 50554510012.

It is a cyclic number.

It is not a de Polignac number, because 21001545505 - 2¹ = 21001545503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21001545503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 407925 + ... + 456514.

It is an arithmetic number, because the mean of its divisors is an integer number (1626011640).

Almost surely, 2^21001545505 is an apocalyptic number.

It is an amenable number.

21001545505 is a deficient number, since it is larger than the sum of its proper divisors (5014640735).

21001545505 is a wasteful number, since it uses less digits than its factorization.

21001545505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 864600.

The product of its (nonzero) digits is 5000, while the sum is 28.

The spelling of 21001545505 in words is "twenty-one billion, one million, five hundred forty-five thousand, five hundred five".