21405006031 has 4 divisors (see below), whose sum is σ = 21515912992. Its totient is φ = 21294099072.

The previous prime is 21405006023. The next prime is 21405006059. The reversal of 21405006031 is 13060050412.

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 21405006031 - 2³ = 21405006023 is a prime.

It is a super-2 number, since 2×21405006031² (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 = 21405005993 and 21405006011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405006001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55453191 + ... + 55453576.

It is an arithmetic number, because the mean of its divisors is an integer number (5378978248).

Almost surely, 2^21405006031 is an apocalyptic number.

21405006031 is a deficient number, since it is larger than the sum of its proper divisors (110906961).

21405006031 is a wasteful number, since it uses less digits than its factorization.

21405006031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110906960.

The product of its (nonzero) digits is 720, while the sum is 22.

Adding to 21405006031 its reverse (13060050412), we get a palindrome (34465056443).

The spelling of 21405006031 in words is "twenty-one billion, four hundred five million, six thousand, thirty-one".