640477421 has 2 divisors, whose sum is σ = 640477422. Its totient is φ = 640477420.

The previous prime is 640477417. The next prime is 640477423. The reversal of 640477421 is 124774046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 493461796 + 147015625 = 22214^2 + 12125^2 .

It is a cyclic number.

It is not a de Polignac number, because 640477421 - 2² = 640477417 is a prime.

It is a super-2 number, since 2×640477421² = 820422653621622482, which contains 22 as substring.

Together with 640477423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640477423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320238710 + 320238711.

It is an arithmetic number, because the mean of its divisors is an integer number (320238711).

Almost surely, 2^640477421 is an apocalyptic number.

It is an amenable number.

640477421 is a deficient number, since it is larger than the sum of its proper divisors (1).

640477421 is an equidigital number, since it uses as much as digits as its factorization.

640477421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37632, while the sum is 35.

The square root of 640477421 is about 25307.6553833025. The cubic root of 640477421 is about 861.9881086604.

The spelling of 640477421 in words is "six hundred forty million, four hundred seventy-seven thousand, four hundred twenty-one".