21521663407 has 2 divisors, whose sum is σ = 21521663408. Its totient is φ = 21521663406.

The previous prime is 21521663399. The next prime is 21521663447. The reversal of 21521663407 is 70436612512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21521663407 - 2³ = 21521663399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21521663447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760831703 + 10760831704.

It is an arithmetic number, because the mean of its divisors is an integer number (10760831704).

Almost surely, 2^21521663407 is an apocalyptic number.

21521663407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521663407 is an equidigital number, since it uses as much as digits as its factorization.

21521663407 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 60480, while the sum is 37.

The spelling of 21521663407 in words is "twenty-one billion, five hundred twenty-one million, six hundred sixty-three thousand, four hundred seven".