21121515220651 has 16 divisors (see below), whose sum is σ = 22408147022400. Its totient is φ = 19839831408640.

The previous prime is 21121515220643. The next prime is 21121515220657. The reversal of 21121515220651 is 15602251512112.

It is a cyclic number.

It is not a de Polignac number, because 21121515220651 - 2³ = 21121515220643 is a prime.

It is a super-2 number, since 2×21121515220651² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121515220657) 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, 17215275 + ... + 18401323.

It is an arithmetic number, because the mean of its divisors is an integer number (1400509188900).

Almost surely, 2^{21121515220651} is an apocalyptic number.

21121515220651 is a deficient number, since it is larger than the sum of its proper divisors (1286631801749).

21121515220651 is a wasteful number, since it uses less digits than its factorization.

21121515220651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1188134.

The product of its (nonzero) digits is 12000, while the sum is 34.

Adding to 21121515220651 its reverse (15602251512112), we get a palindrome (36723766732763).

The spelling of 21121515220651 in words is "twenty-one trillion, one hundred twenty-one billion, five hundred fifteen million, two hundred twenty thousand, six hundred fifty-one".