21154521031566 has 32 divisors (see below), whose sum is σ = 45799664537760. Its totient is φ = 6475357569024.

The previous prime is 21154521031561. The next prime is 21154521031663. The reversal of 21154521031566 is 66513012545112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154521031561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 702606211 + ... + 702636318.

It is an arithmetic number, because the mean of its divisors is an integer number (1431239516805).

Almost surely, 2^{21154521031566} is an apocalyptic number.

21154521031566 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21154521031566 is an abundant number, since it is smaller than the sum of its proper divisors (24645143506194).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21154521031566 is a wasteful number, since it uses less digits than its factorization.

21154521031566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1405242740.

The product of its (nonzero) digits is 216000, while the sum is 42.

Adding to 21154521031566 its reverse (66513012545112), we get a palindrome (87667533576678).

The spelling of 21154521031566 in words is "twenty-one trillion, one hundred fifty-four billion, five hundred twenty-one million, thirty-one thousand, five hundred sixty-six".