20671521 has 16 divisors (see below), whose sum is σ = 29776320. Its totient is φ = 12680640.

The previous prime is 20671517. The next prime is 20671529. The reversal of 20671521 is 12517602.

It is not a de Polignac number, because 20671521 - 2² = 20671517 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20671491 and 20671500.

It is not an unprimeable number, because it can be changed into a prime (20671529) 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, 15790 + ... + 17048.

It is an arithmetic number, because the mean of its divisors is an integer number (1861020).

Almost surely, 2^20671521 is an apocalyptic number.

It is an amenable number.

20671521 is a deficient number, since it is larger than the sum of its proper divisors (9104799).

20671521 is a wasteful number, since it uses less digits than its factorization.

20671521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1696.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 20671521 is about 4546.5944397978. The cubic root of 20671521 is about 274.4463616285.

The spelling of 20671521 in words is "twenty million, six hundred seventy-one thousand, five hundred twenty-one".