21571641 has 24 divisors (see below), whose sum is σ = 38351040. Its totient is φ = 11378016.

The previous prime is 21571607. The next prime is 21571651. The reversal of 21571641 is 14617512.

It is a happy number.

21571641 is a `hidden beast` number, since 2 + 15 + 7 + 1 + 641 = 666.

It is not a de Polignac number, because 21571641 - 2⁶ = 21571577 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21571651) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12351 + ... + 13988.

It is an arithmetic number, because the mean of its divisors is an integer number (1597960).

Almost surely, 2^21571641 is an apocalyptic number.

21571641 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21571641 is a deficient number, since it is larger than the sum of its proper divisors (16779399).

21571641 is a wasteful number, since it uses less digits than its factorization.

21571641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26365 (or 26362 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 21571641 is about 4644.5280707516. The cubic root of 21571641 is about 278.3733962514.

The spelling of 21571641 in words is "twenty-one million, five hundred seventy-one thousand, six hundred forty-one".