21571578645 has 32 divisors (see below), whose sum is σ = 34658928000. Its totient is φ = 11456815104.

The previous prime is 21571578641. The next prime is 21571578649. The reversal of 21571578645 is 54687517512.

It is an interprime number because it is at equal distance from previous prime (21571578641) and next prime (21571578649).

It is not a de Polignac number, because 21571578645 - 2² = 21571578641 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21571578641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3788961 + ... + 3794649.

It is an arithmetic number, because the mean of its divisors is an integer number (1083091500).

Almost surely, 2^21571578645 is an apocalyptic number.

It is an amenable number.

21571578645 is a deficient number, since it is larger than the sum of its proper divisors (13087349355).

21571578645 is a wasteful number, since it uses less digits than its factorization.

21571578645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6709.

The product of its digits is 2352000, while the sum is 51.

The spelling of 21571578645 in words is "twenty-one billion, five hundred seventy-one million, five hundred seventy-eight thousand, six hundred forty-five".