21521666007 has 16 divisors (see below), whose sum is σ = 33270209280. Its totient is φ = 13723960536.

The previous prime is 21521665943. The next prime is 21521666011. The reversal of 21521666007 is 70066612512.

It is a happy number.

It is not a de Polignac number, because 21521666007 - 2⁶ = 21521665943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521666027) 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, 17327613 + ... + 17328854.

It is an arithmetic number, because the mean of its divisors is an integer number (2079388080).

Almost surely, 2^21521666007 is an apocalyptic number.

21521666007 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21521666007 is a deficient number, since it is larger than the sum of its proper divisors (11748543273).

21521666007 is a wasteful number, since it uses less digits than its factorization.

21521666007 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34656499 (or 34656493 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The spelling of 21521666007 in words is "twenty-one billion, five hundred twenty-one million, six hundred sixty-six thousand, seven".