20481821 has 4 divisors (see below), whose sum is σ = 21686652. Its totient is φ = 19276992.

The previous prime is 20481817. The next prime is 20481823. The reversal of 20481821 is 12818402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12818402 = 2 ⋅6409201.

It can be written as a sum of positive squares in 2 ways, for example, as 14668900 + 5812921 = 3830^2 + 2411^2 .

It is a cyclic number.

It is not a de Polignac number, because 20481821 - 2² = 20481817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20481823) 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, 602390 + ... + 602423.

It is an arithmetic number, because the mean of its divisors is an integer number (5421663).

Almost surely, 2^20481821 is an apocalyptic number.

It is an amenable number.

20481821 is a deficient number, since it is larger than the sum of its proper divisors (1204831).

20481821 is a wasteful number, since it uses less digits than its factorization.

20481821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1204830.

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 20481821 is about 4525.6845890981. The cubic root of 20481821 is about 273.6042602545.

The spelling of 20481821 in words is "twenty million, four hundred eighty-one thousand, eight hundred twenty-one".