21505332401 has 16 divisors (see below), whose sum is σ = 26063823744. Its totient is φ = 17321796864.

The previous prime is 21505332379. The next prime is 21505332439. The reversal of 21505332401 is 10423350512.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21505332401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21505332451) 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, 64010 + ... + 217043.

It is an arithmetic number, because the mean of its divisors is an integer number (1628988984).

Almost surely, 2^21505332401 is an apocalyptic number.

It is an amenable number.

21505332401 is a deficient number, since it is larger than the sum of its proper divisors (4558491343).

21505332401 is a wasteful number, since it uses less digits than its factorization.

21505332401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281720.

The product of its (nonzero) digits is 3600, while the sum is 26.

Adding to 21505332401 its reverse (10423350512), we get a palindrome (31928682913).

The spelling of 21505332401 in words is "twenty-one billion, five hundred five million, three hundred thirty-two thousand, four hundred one".