21906949 has 2 divisors, whose sum is σ = 21906950. Its totient is φ = 21906948.

The previous prime is 21906917. The next prime is 21906953. The reversal of 21906949 is 94960912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20657025 + 1249924 = 4545^2 + 1118^2 .

It is a cyclic number.

It is not a de Polignac number, because 21906949 - 2⁵ = 21906917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (24906949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953474 + 10953475.

It is an arithmetic number, because the mean of its divisors is an integer number (10953475).

Almost surely, 2^21906949 is an apocalyptic number.

It is an amenable number.

21906949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906949 is an equidigital number, since it uses as much as digits as its factorization.

21906949 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34992, while the sum is 40.

The square root of 21906949 is about 4680.4859790411. The cubic root of 21906949 is about 279.8083254514.

The spelling of 21906949 in words is "twenty-one million, nine hundred six thousand, nine hundred forty-nine".