20501156421 has 18 divisors (see below), whose sum is σ = 30956279718. Its totient is φ = 13073198160.

The previous prime is 20501156413. The next prime is 20501156449. The reversal of 20501156421 is 12465110502.

20501156421 is a `hidden beast` number, since 2 + 0 + 5 + 0 + 1 + 15 + 642 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19716372225 + 784784196 = 140415^2 + 28014^2 .

It is not a de Polignac number, because 20501156421 - 2³ = 20501156413 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20501156461) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 2148270 + ... + 2157791.

Almost surely, 2^20501156421 is an apocalyptic number.

It is an amenable number.

20501156421 is a deficient number, since it is larger than the sum of its proper divisors (10455123297).

20501156421 is a wasteful number, since it uses less digits than its factorization.

20501156421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4306113 (or 4306087 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

Adding to 20501156421 its reverse (12465110502), we get a palindrome (32966266923).

The spelling of 20501156421 in words is "twenty billion, five hundred one million, one hundred fifty-six thousand, four hundred twenty-one".