20521540251 has 24 divisors (see below), whose sum is σ = 31493152080. Its totient is φ = 12852254016.

The previous prime is 20521540243. The next prime is 20521540261. The reversal of 20521540251 is 15204512502.

20521540251 is a `hidden beast` number, since 20 + 52 + 1 + 540 + 2 + 51 = 666.

It is not a de Polignac number, because 20521540251 - 2³ = 20521540243 is a prime.

It is a super-2 number, since 2×20521540251² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20521540231) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1052865 + ... + 1072178.

It is an arithmetic number, because the mean of its divisors is an integer number (1312214670).

Almost surely, 2^20521540251 is an apocalyptic number.

20521540251 is a deficient number, since it is larger than the sum of its proper divisors (10971611829).

20521540251 is a wasteful number, since it uses less digits than its factorization.

20521540251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2125115 (or 2125112 counting only the distinct ones).

The product of its (nonzero) digits is 4000, while the sum is 27.

The spelling of 20521540251 in words is "twenty billion, five hundred twenty-one million, five hundred forty thousand, two hundred fifty-one".