21125142631 has 4 divisors (see below), whose sum is σ = 21235745664. Its totient is φ = 21014539600.

The previous prime is 21125142613. The next prime is 21125142671. The reversal of 21125142631 is 13624152112.

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 21125142631 - 2⁷ = 21125142503 is a prime.

It is a super-2 number, since 2×21125142631² (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 21125142631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125142611) 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, 55301230 + ... + 55301611.

It is an arithmetic number, because the mean of its divisors is an integer number (5308936416).

Almost surely, 2^21125142631 is an apocalyptic number.

21125142631 is a deficient number, since it is larger than the sum of its proper divisors (110603033).

21125142631 is a wasteful number, since it uses less digits than its factorization.

21125142631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110603032.

The product of its digits is 2880, while the sum is 28.

Adding to 21125142631 its reverse (13624152112), we get a palindrome (34749294743).

The spelling of 21125142631 in words is "twenty-one billion, one hundred twenty-five million, one hundred forty-two thousand, six hundred thirty-one".