405981621 has 12 divisors (see below), whose sum is σ = 594678240. Its totient is φ = 266841960.

The previous prime is 405981617. The next prime is 405981637. The reversal of 405981621 is 126189504.

405981621 is a `hidden beast` number, since 4 + 0 + 598 + 1 + 62 + 1 = 666.

It is not a de Polignac number, because 405981621 - 2² = 405981617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405981601) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 317031 + ... + 318308.

It is an arithmetic number, because the mean of its divisors is an integer number (49556520).

Almost surely, 2^405981621 is an apocalyptic number.

It is an amenable number.

405981621 is a deficient number, since it is larger than the sum of its proper divisors (188696619).

405981621 is a wasteful number, since it uses less digits than its factorization.

405981621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635416 (or 635413 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 405981621 is about 20148.9856072210. The cubic root of 405981621 is about 740.4608895371.

The spelling of 405981621 in words is "four hundred five million, nine hundred eighty-one thousand, six hundred twenty-one".