21216016166451 has 4 divisors (see below), whose sum is σ = 28288021555272. Its totient is φ = 14144010777632.

The previous prime is 21216016166437. The next prime is 21216016166461. The reversal of 21216016166451 is 15466161061212.

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 21216016166451 - 2¹⁰ = 21216016165427 is a prime.

It is a super-2 number, since 2×21216016166451² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21216016166461) 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, 3536002694406 + ... + 3536002694411.

It is an arithmetic number, because the mean of its divisors is an integer number (7072005388818).

Almost surely, 2^{21216016166451} is an apocalyptic number.

21216016166451 is a deficient number, since it is larger than the sum of its proper divisors (7072005388821).

21216016166451 is an equidigital number, since it uses as much as digits as its factorization.

21216016166451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7072005388820.

The product of its (nonzero) digits is 103680, while the sum is 42.

The spelling of 21216016166451 in words is "twenty-one trillion, two hundred sixteen billion, sixteen million, one hundred sixty-six thousand, four hundred fifty-one".