21256006253 has 4 divisors (see below), whose sum is σ = 22506359580. Its totient is φ = 20005652928.

The previous prime is 21256006237. The next prime is 21256006271. The reversal of 21256006253 is 35260065212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16942406569 + 4313599684 = 130163^2 + 65678^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256006253 - 2⁴ = 21256006237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256006223) 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, 625176638 + ... + 625176671.

It is an arithmetic number, because the mean of its divisors is an integer number (5626589895).

Almost surely, 2^21256006253 is an apocalyptic number.

It is an amenable number.

21256006253 is a deficient number, since it is larger than the sum of its proper divisors (1250353327).

21256006253 is a wasteful number, since it uses less digits than its factorization.

21256006253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1250353326.

The product of its (nonzero) digits is 21600, while the sum is 32.

The spelling of 21256006253 in words is "twenty-one billion, two hundred fifty-six million, six thousand, two hundred fifty-three".