20401691 has 2 divisors, whose sum is σ = 20401692. Its totient is φ = 20401690.

The previous prime is 20401663. The next prime is 20401709. The reversal of 20401691 is 19610402.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20401691 is a prime.

It is not a weakly prime, because it can be changed into another prime (20401291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10200845 + 10200846.

It is an arithmetic number, because the mean of its divisors is an integer number (10200846).

Almost surely, 2^20401691 is an apocalyptic number.

20401691 is a deficient number, since it is larger than the sum of its proper divisors (1).

20401691 is an equidigital number, since it uses as much as digits as its factorization.

20401691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 20401691 is about 4516.8231092218. The cubic root of 20401691 is about 273.2469912031.

The spelling of 20401691 in words is "twenty million, four hundred one thousand, six hundred ninety-one".