2115721 has 2 divisors, whose sum is σ = 2115722. Its totient is φ = 2115720.

The previous prime is 2115713. The next prime is 2115727. The reversal of 2115721 is 1275112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1742400 + 373321 = 1320^2 + 611^2 .

It is a cyclic number.

It is not a de Polignac number, because 2115721 - 2³ = 2115713 is a prime.

It is not a weakly prime, because it can be changed into another prime (2115727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1057860 + 1057861.

It is an arithmetic number, because the mean of its divisors is an integer number (1057861).

2^2115721 is an apocalyptic number.

It is an amenable number.

2115721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2115721 is an equidigital number, since it uses as much as digits as its factorization.

2115721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 140, while the sum is 19.

The square root of 2115721 is about 1454.5518210088. The cubic root of 2115721 is about 128.3766776997.

The spelling of 2115721 in words is "two million, one hundred fifteen thousand, seven hundred twenty-one".