1604907721 has 2 divisors, whose sum is σ = 1604907722. Its totient is φ = 1604907720.

The previous prime is 1604907697. The next prime is 1604907739. The reversal of 1604907721 is 1277094061.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1588819600 + 16088121 = 39860^2 + 4011^2 .

It is a cyclic number.

It is not a de Polignac number, because 1604907721 - 2¹³ = 1604899529 is a prime.

It is not a weakly prime, because it can be changed into another prime (1604907221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 802453860 + 802453861.

It is an arithmetic number, because the mean of its divisors is an integer number (802453861).

Almost surely, 2^1604907721 is an apocalyptic number.

It is an amenable number.

1604907721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1604907721 is an equidigital number, since it uses as much as digits as its factorization.

1604907721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21168, while the sum is 37.

The square root of 1604907721 is about 40061.2995420768. The cubic root of 1604907721 is about 1170.8017299435.

The spelling of 1604907721 in words is "one billion, six hundred four million, nine hundred seven thousand, seven hundred twenty-one".