21156045601 has 4 divisors (see below), whose sum is σ = 21156692500. Its totient is φ = 21155398704.

The previous prime is 21156045571. The next prime is 21156045649. The reversal of 21156045601 is 10654065112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16015155601 + 5140890000 = 126551^2 + 71700^2 .

It is a cyclic number.

It is not a de Polignac number, because 21156045601 - 2⁷ = 21156045473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156045661) 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, 271626 + ... + 340723.

It is an arithmetic number, because the mean of its divisors is an integer number (5289173125).

Almost surely, 2^21156045601 is an apocalyptic number.

It is an amenable number.

21156045601 is a deficient number, since it is larger than the sum of its proper divisors (646899).

21156045601 is an equidigital number, since it uses as much as digits as its factorization.

21156045601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646898.

The product of its (nonzero) digits is 7200, while the sum is 31.

The spelling of 21156045601 in words is "twenty-one billion, one hundred fifty-six million, forty-five thousand, six hundred one".