21506777544651 has 16 divisors (see below), whose sum is σ = 32773918798848. Its totient is φ = 12288954787200.

The previous prime is 21506777544613. The next prime is 21506777544727. The reversal of 21506777544651 is 15644577760512.

It is not a de Polignac number, because 21506777544651 - 2¹⁴ = 21506777528267 is a prime.

It is a super-3 number, since 3×21506777544651³ (a number of 41 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21506777544601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25931235 + ... + 26747756.

It is an arithmetic number, because the mean of its divisors is an integer number (2048369924928).

Almost surely, 2^{21506777544651} is an apocalyptic number.

21506777544651 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21506777544651 is a deficient number, since it is larger than the sum of its proper divisors (11267141254197).

21506777544651 is a wasteful number, since it uses less digits than its factorization.

21506777544651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52698442.

The product of its (nonzero) digits is 49392000, while the sum is 60.

The spelling of 21506777544651 in words is "twenty-one trillion, five hundred six billion, seven hundred seventy-seven million, five hundred forty-four thousand, six hundred fifty-one".