21571949 has 16 divisors (see below), whose sum is σ = 25256448. Its totient is φ = 18044592.

The previous prime is 21571943. The next prime is 21571961. The reversal of 21571949 is 94917512.

It is a cyclic number.

It is not a de Polignac number, because 21571949 - 2⁴ = 21571933 is a prime.

It is a Curzon number.

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21571943) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 61994 + ... + 62340.

It is an arithmetic number, because the mean of its divisors is an integer number (1578528).

Almost surely, 2^21571949 is an apocalyptic number.

It is an amenable number.

21571949 is a deficient number, since it is larger than the sum of its proper divisors (3684499).

21571949 is a wasteful number, since it uses less digits than its factorization.

21571949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544.

The product of its digits is 22680, while the sum is 38.

The square root of 21571949 is about 4644.5612279310. The cubic root of 21571949 is about 278.3747211174.

The spelling of 21571949 in words is "twenty-one million, five hundred seventy-one thousand, nine hundred forty-nine".