21402123431 has 32 divisors (see below), whose sum is σ = 24455471040. Its totient is φ = 18567097344.

The previous prime is 21402123427. The next prime is 21402123437. The reversal of 21402123431 is 13432120412.

It is a cyclic number.

It is not a de Polignac number, because 21402123431 - 2² = 21402123427 is a prime.

It is a super-2 number, since 2×21402123431² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21402123397 and 21402123406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21402123437) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 21466025 + ... + 21467021.

It is an arithmetic number, because the mean of its divisors is an integer number (764233470).

Almost surely, 2^21402123431 is an apocalyptic number.

21402123431 is a deficient number, since it is larger than the sum of its proper divisors (3053347609).

21402123431 is a wasteful number, since it uses less digits than its factorization.

21402123431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1635.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21402123431 its reverse (13432120412), we get a palindrome (34834243843).

The spelling of 21402123431 in words is "twenty-one billion, four hundred two million, one hundred twenty-three thousand, four hundred thirty-one".