21901321601 has 4 divisors (see below), whose sum is σ = 22178553600. Its totient is φ = 21624089604.

The previous prime is 21901321597. The next prime is 21901321621. The reversal of 21901321601 is 10612310912.

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 21901321601 - 2² = 21901321597 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21901321621) 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, 138615881 + ... + 138616038.

It is an arithmetic number, because the mean of its divisors is an integer number (5544638400).

Almost surely, 2^21901321601 is an apocalyptic number.

It is an amenable number.

21901321601 is a deficient number, since it is larger than the sum of its proper divisors (277231999).

21901321601 is an equidigital number, since it uses as much as digits as its factorization.

21901321601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277231998.

The product of its (nonzero) digits is 648, while the sum is 26.

The spelling of 21901321601 in words is "twenty-one billion, nine hundred one million, three hundred twenty-one thousand, six hundred one".