20511921 has 8 divisors (see below), whose sum is σ = 27797824. Its totient is φ = 13450320.

The previous prime is 20511913. The next prime is 20511923. The reversal of 20511921 is 12911502.

20511921 is nontrivially palindromic in base 4.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20511921 - 2³ = 20511913 is a prime.

It is a super-2 number, since 2×20511921² = 841477806220482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20511923) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55861 + ... + 56226.

It is an arithmetic number, because the mean of its divisors is an integer number (3474728).

Almost surely, 2^20511921 is an apocalyptic number.

It is an amenable number.

20511921 is a deficient number, since it is larger than the sum of its proper divisors (7285903).

20511921 is a wasteful number, since it uses less digits than its factorization.

20511921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112151.

The product of its (nonzero) digits is 180, while the sum is 21.

The square root of 20511921 is about 4529.0088319631. The cubic root of 20511921 is about 273.7382238841.

The spelling of 20511921 in words is "twenty million, five hundred eleven thousand, nine hundred twenty-one".