20137921 has 4 divisors (see below), whose sum is σ = 20148100. Its totient is φ = 20127744.

The previous prime is 20137913. The next prime is 20137951. The reversal of 20137921 is 12973102.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 4456321 + 15681600 = 2111^2 + 3960^2 .

It is a cyclic number.

It is not a de Polignac number, because 20137921 - 2³ = 20137913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20137951) 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, 1056 + ... + 6433.

It is an arithmetic number, because the mean of its divisors is an integer number (5037025).

Almost surely, 2^20137921 is an apocalyptic number.

It is an amenable number.

20137921 is a deficient number, since it is larger than the sum of its proper divisors (10179).

20137921 is an equidigital number, since it uses as much as digits as its factorization.

20137921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10178.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 20137921 is about 4487.5294985103. The cubic root of 20137921 is about 272.0642914994.

The spelling of 20137921 in words is "twenty million, one hundred thirty-seven thousand, nine hundred twenty-one".