21505332407 has 4 divisors (see below), whose sum is σ = 23159588760. Its totient is φ = 19851076056.

The previous prime is 21505332379. The next prime is 21505332439. The reversal of 21505332407 is 70423350512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21505332407 - 2⁸ = 21505332151 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 (21505332467) 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, 827128157 + ... + 827128182.

It is an arithmetic number, because the mean of its divisors is an integer number (5789897190).

Almost surely, 2^21505332407 is an apocalyptic number.

21505332407 is a deficient number, since it is larger than the sum of its proper divisors (1654256353).

21505332407 is a wasteful number, since it uses less digits than its factorization.

21505332407 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1654256352.

The product of its (nonzero) digits is 25200, while the sum is 32.

Adding to 21505332407 its reverse (70423350512), we get a palindrome (91928682919).

The spelling of 21505332407 in words is "twenty-one billion, five hundred five million, three hundred thirty-two thousand, four hundred seven".