21161003213506 has 16 divisors (see below), whose sum is σ = 34183254027384. Its totient is φ = 9766589727744.

The previous prime is 21161003213491. The next prime is 21161003213551. The reversal of 21161003213506 is 60531230016112.

It can be written as a sum of positive squares in 4 ways, for example, as 14758205572881 + 6402797640625 = 3841641^2 + 2530375^2 .

It is a super-2 number, since 2×21161003213506² (a number of 27 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10767586 + ... + 12580258.

Almost surely, 2^{21161003213506} is an apocalyptic number.

21161003213506 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21161003213506 is a deficient number, since it is larger than the sum of its proper divisors (13022250813878).

21161003213506 is a wasteful number, since it uses less digits than its factorization.

21161003213506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2261685.

The product of its (nonzero) digits is 6480, while the sum is 31.

Adding to 21161003213506 its reverse (60531230016112), we get a palindrome (81692233229618).

The spelling of 21161003213506 in words is "twenty-one trillion, one hundred sixty-one billion, three million, two hundred thirteen thousand, five hundred six".