21420520031 has 4 divisors (see below), whose sum is σ = 21421984200. Its totient is φ = 21419055864.

The previous prime is 21420520021. The next prime is 21420520049. The reversal of 21420520031 is 13002502412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21420520031 is a prime.

It is a super-2 number, since 2×21420520031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420519985 and 21420520012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420520021) 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, 709916 + ... + 739473.

It is an arithmetic number, because the mean of its divisors is an integer number (5355496050).

Almost surely, 2^21420520031 is an apocalyptic number.

21420520031 is a deficient number, since it is larger than the sum of its proper divisors (1464169).

21420520031 is a wasteful number, since it uses less digits than its factorization.

21420520031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1464168.

The product of its (nonzero) digits is 480, while the sum is 20.

The spelling of 21420520031 in words is "twenty-one billion, four hundred twenty million, five hundred twenty thousand, thirty-one".