21521606261 has 16 divisors (see below), whose sum is σ = 22901524800. Its totient is φ = 20167056000.

The previous prime is 21521606251. The next prime is 21521606273. The reversal of 21521606261 is 16260612512.

It is not a de Polignac number, because 21521606261 - 2²² = 21517411957 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 (21521606251) 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, 1236026 + ... + 1253316.

It is an arithmetic number, because the mean of its divisors is an integer number (1431345300).

Almost surely, 2^21521606261 is an apocalyptic number.

It is an amenable number.

21521606261 is a deficient number, since it is larger than the sum of its proper divisors (1379918539).

21521606261 is a wasteful number, since it uses less digits than its factorization.

21521606261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18020.

The product of its (nonzero) digits is 8640, while the sum is 32.

The spelling of 21521606261 in words is "twenty-one billion, five hundred twenty-one million, six hundred six thousand, two hundred sixty-one".