21520404101 has 16 divisors (see below), whose sum is σ = 24682896000. Its totient is φ = 18380029248.

The previous prime is 21520404067. The next prime is 21520404107. The reversal of 21520404101 is 10140402512.

It is a happy number.

It is not a de Polignac number, because 21520404101 - 2¹⁸ = 21520141957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520404107) 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, 5086655 + ... + 5090883.

It is an arithmetic number, because the mean of its divisors is an integer number (1542681000).

Almost surely, 2^21520404101 is an apocalyptic number.

It is an amenable number.

21520404101 is a deficient number, since it is larger than the sum of its proper divisors (3162491899).

21520404101 is a wasteful number, since it uses less digits than its factorization.

21520404101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6668.

The product of its (nonzero) digits is 320, while the sum is 20.

Adding to 21520404101 its reverse (10140402512), we get a palindrome (31660806613).

The spelling of 21520404101 in words is "twenty-one billion, five hundred twenty million, four hundred four thousand, one hundred one".