21005631431 has 4 divisors (see below), whose sum is σ = 22111191000. Its totient is φ = 19900071864.

The previous prime is 21005631419. The next prime is 21005631461. The reversal of 21005631431 is 13413650012.

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 21005631431 - 2¹⁴ = 21005615047 is a prime.

It is a super-2 number, since 2×21005631431² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21005631431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005631461) 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, 552779756 + ... + 552779793.

It is an arithmetic number, because the mean of its divisors is an integer number (5527797750).

Almost surely, 2^21005631431 is an apocalyptic number.

21005631431 is a deficient number, since it is larger than the sum of its proper divisors (1105559569).

21005631431 is a wasteful number, since it uses less digits than its factorization.

21005631431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1105559568.

The product of its (nonzero) digits is 2160, while the sum is 26.

The spelling of 21005631431 in words is "twenty-one billion, five million, six hundred thirty-one thousand, four hundred thirty-one".