21572737 has 4 divisors (see below), whose sum is σ = 21634900. Its totient is φ = 21510576.

The previous prime is 21572729. The next prime is 21572753. The reversal of 21572737 is 73727512.

It is a happy number.

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 16573041 + 4999696 = 4071^2 + 2236^2 .

It is a cyclic number.

It is not a de Polignac number, because 21572737 - 2³ = 21572729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21572237) 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, 30558 + ... + 31255.

It is an arithmetic number, because the mean of its divisors is an integer number (5408725).

Almost surely, 2^21572737 is an apocalyptic number.

It is an amenable number.

21572737 is a deficient number, since it is larger than the sum of its proper divisors (62163).

21572737 is an equidigital number, since it uses as much as digits as its factorization.

21572737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62162.

The product of its digits is 20580, while the sum is 34.

The square root of 21572737 is about 4644.6460575592. The cubic root of 21572737 is about 278.3781106521.

The spelling of 21572737 in words is "twenty-one million, five hundred seventy-two thousand, seven hundred thirty-seven".