21020977 has 4 divisors (see below), whose sum is σ = 21213940. Its totient is φ = 20828016.

The previous prime is 21020971. The next prime is 21021001. The reversal of 21020977 is 77902012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15023376 + 5997601 = 3876^2 + 2449^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020977 - 2⁷ = 21020849 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21020971) 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, 96318 + ... + 96535.

It is an arithmetic number, because the mean of its divisors is an integer number (5303485).

Almost surely, 2^21020977 is an apocalyptic number.

It is an amenable number.

21020977 is a deficient number, since it is larger than the sum of its proper divisors (192963).

21020977 is a wasteful number, since it uses less digits than its factorization.

21020977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192962.

The product of its (nonzero) digits is 1764, while the sum is 28.

The square root of 21020977 is about 4584.8639020150. The cubic root of 21020977 is about 275.9842504841.

Adding to 21020977 its reverse (77902012), we get a palindrome (98922989).

The spelling of 21020977 in words is "twenty-one million, twenty thousand, nine hundred seventy-seven".