20977861 has 2 divisors, whose sum is σ = 20977862. Its totient is φ = 20977860.

The previous prime is 20977849. The next prime is 20977871. The reversal of 20977861 is 16877902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14822500 + 6155361 = 3850^2 + 2481^2 .

It is a cyclic number.

It is not a de Polignac number, because 20977861 - 2²³ = 12589253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20977811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10488930 + 10488931.

It is an arithmetic number, because the mean of its divisors is an integer number (10488931).

Almost surely, 2^20977861 is an apocalyptic number.

It is an amenable number.

20977861 is a deficient number, since it is larger than the sum of its proper divisors (1).

20977861 is an equidigital number, since it uses as much as digits as its factorization.

20977861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 20977861 is about 4580.1594950394. The cubic root of 20977861 is about 275.7954314490.

The spelling of 20977861 in words is "twenty million, nine hundred seventy-seven thousand, eight hundred sixty-one".