21256042163437 has 8 divisors (see below), whose sum is σ = 21989062661400. Its totient is φ = 20523025233984.

The previous prime is 21256042163431. The next prime is 21256042163441. The reversal of 21256042163437 is 73436124065212.

It can be written as a sum of positive squares in 4 ways, for example, as 10288062665001 + 10967979498436 = 3207501^2 + 3311794^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21256042163437 - 2³¹ = 21253894679789 is a prime.

It is a super-2 number, since 2×21256042163437² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256042163431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18026739 + ... + 19169647.

It is an arithmetic number, because the mean of its divisors is an integer number (2748632832675).

Almost surely, 2^{21256042163437} is an apocalyptic number.

It is an amenable number.

21256042163437 is a deficient number, since it is larger than the sum of its proper divisors (733020497963).

21256042163437 is a wasteful number, since it uses less digits than its factorization.

21256042163437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1784255.

The product of its (nonzero) digits is 1451520, while the sum is 46.

It can be divided in two parts, 2125604 and 2163437, that added together give a square (4289041 = 2071²).

The spelling of 21256042163437 in words is "twenty-one trillion, two hundred fifty-six billion, forty-two million, one hundred sixty-three thousand, four hundred thirty-seven".