20947621 has 4 divisors (see below), whose sum is σ = 22179852. Its totient is φ = 19715392.

The previous prime is 20947613. The next prime is 20947631. The reversal of 20947621 is 12674902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12674902 = 2 ⋅6337451.

It can be written as a sum of positive squares in 2 ways, for example, as 8767521 + 12180100 = 2961^2 + 3490^2 .

It is a cyclic number.

It is not a de Polignac number, because 20947621 - 2³ = 20947613 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 (20947631) 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, 616090 + ... + 616123.

It is an arithmetic number, because the mean of its divisors is an integer number (5544963).

Almost surely, 2^20947621 is an apocalyptic number.

It is an amenable number.

20947621 is a deficient number, since it is larger than the sum of its proper divisors (1232231).

20947621 is a wasteful number, since it uses less digits than its factorization.

20947621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1232230.

The product of its (nonzero) digits is 6048, while the sum is 31.

The square root of 20947621 is about 4576.8571094147. The cubic root of 20947621 is about 275.6628462042.

The spelling of 20947621 in words is "twenty million, nine hundred forty-seven thousand, six hundred twenty-one".