21311957801 has 4 divisors (see below), whose sum is σ = 21312512400. Its totient is φ = 21311403204.

The previous prime is 21311957767. The next prime is 21311957833. The reversal of 21311957801 is 10875911312.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21311957801 - 2³⁴ = 4132088617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311957101) 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, 214991 + ... + 298068.

It is an arithmetic number, because the mean of its divisors is an integer number (5328128100).

Almost surely, 2^21311957801 is an apocalyptic number.

It is an amenable number.

21311957801 is a deficient number, since it is larger than the sum of its proper divisors (554599).

21311957801 is an equidigital number, since it uses as much as digits as its factorization.

21311957801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 554598.

The product of its (nonzero) digits is 15120, while the sum is 38.

The spelling of 21311957801 in words is "twenty-one billion, three hundred eleven million, nine hundred fifty-seven thousand, eight hundred one".