21515520434231 has 4 divisors (see below), whose sum is σ = 21517602658872. Its totient is φ = 21513438209592.

The previous prime is 21515520434171. The next prime is 21515520434293. The reversal of 21515520434231 is 13243402551512.

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

It is a cyclic number.

It is not a de Polignac number, because 21515520434231 - 2¹⁸ = 21515520172087 is a prime.

It is a super-2 number, since 2×21515520434231² (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 (21515520434831) 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, 1041096821 + ... + 1041117486.

It is an arithmetic number, because the mean of its divisors is an integer number (5379400664718).

Almost surely, 2^{21515520434231} is an apocalyptic number.

21515520434231 is a deficient number, since it is larger than the sum of its proper divisors (2082224641).

21515520434231 is a wasteful number, since it uses less digits than its factorization.

21515520434231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2082224640.

The product of its (nonzero) digits is 144000, while the sum is 38.

Adding to 21515520434231 its reverse (13243402551512), we get a palindrome (34758922985743).

The spelling of 21515520434231 in words is "twenty-one trillion, five hundred fifteen billion, five hundred twenty million, four hundred thirty-four thousand, two hundred thirty-one".