21251140154 has 4 divisors (see below), whose sum is σ = 31876710234. Its totient is φ = 10625570076.

The previous prime is 21251140133. The next prime is 21251140171. The reversal of 21251140154 is 45104115212.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 21133309129 + 117831025 = 145373^2 + 10855^2 .

It is a super-2 number, since 2×21251140154² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5312785037 + ... + 5312785040.

Almost surely, 2^21251140154 is an apocalyptic number.

21251140154 is a deficient number, since it is larger than the sum of its proper divisors (10625570080).

21251140154 is a wasteful number, since it uses less digits than its factorization.

21251140154 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10625570079.

The product of its (nonzero) digits is 1600, while the sum is 26.

Adding to 21251140154 its reverse (45104115212), we get a palindrome (66355255366).

The spelling of 21251140154 in words is "twenty-one billion, two hundred fifty-one million, one hundred forty thousand, one hundred fifty-four".