21978701 has 2 divisors, whose sum is σ = 21978702. Its totient is φ = 21978700.

The previous prime is 21978673. The next prime is 21978743. The reversal of 21978701 is 10787912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 1503076 = 4525^2 + 1226^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21978701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21978791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10989350 + 10989351.

It is an arithmetic number, because the mean of its divisors is an integer number (10989351).

Almost surely, 2^21978701 is an apocalyptic number.

It is an amenable number.

21978701 is a deficient number, since it is larger than the sum of its proper divisors (1).

21978701 is an equidigital number, since it uses as much as digits as its factorization.

21978701 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 21978701 is about 4688.1447289946. The cubic root of 21978701 is about 280.1134786629.

The spelling of 21978701 in words is "twenty-one million, nine hundred seventy-eight thousand, seven hundred one".