21521041101551 has 4 divisors (see below), whose sum is σ = 21729983248272. Its totient is φ = 21312098954832.

The previous prime is 21521041101533. The next prime is 21521041101557. The reversal of 21521041101551 is 15510114012512.

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 21521041101551 - 2³⁴ = 21503861232367 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 (21521041101557) 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, 104471073206 + ... + 104471073411.

It is an arithmetic number, because the mean of its divisors is an integer number (5432495812068).

Almost surely, 2^{21521041101551} is an apocalyptic number.

21521041101551 is a deficient number, since it is larger than the sum of its proper divisors (208942146721).

21521041101551 is a wasteful number, since it uses less digits than its factorization.

21521041101551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208942146720.

The product of its (nonzero) digits is 2000, while the sum is 29.

The spelling of 21521041101551 in words is "twenty-one trillion, five hundred twenty-one billion, forty-one million, one hundred one thousand, five hundred fifty-one".