21531454251 has 8 divisors (see below), whose sum is σ = 28715670480. Its totient is φ = 14350770432.

The previous prime is 21531454207. The next prime is 21531454279. The reversal of 21531454251 is 15245413512.

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

It is not a de Polignac number, because 21531454251 - 2²² = 21527259947 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21531454201) 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, 868846 + ... + 893283.

It is an arithmetic number, because the mean of its divisors is an integer number (3589458810).

Almost surely, 2^21531454251 is an apocalyptic number.

21531454251 is a deficient number, since it is larger than the sum of its proper divisors (7184216229).

21531454251 is a wasteful number, since it uses less digits than its factorization.

21531454251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1766205.

The product of its digits is 24000, while the sum is 33.

Adding to 21531454251 its reverse (15245413512), we get a palindrome (36776867763).

The spelling of 21531454251 in words is "twenty-one billion, five hundred thirty-one million, four hundred fifty-four thousand, two hundred fifty-one".