64821690 has 24 divisors (see below), whose sum is σ = 168536628. Its totient is φ = 17285760.

The previous prime is 64821667. The next prime is 64821719. The reversal of 64821690 is 9612846.

64821690 is a `hidden beast` number, since 648 + 2 + 1 + 6 + 9 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 62773929 + 2047761 = 7923^2 + 1431^2 .

It is a super-2 number, since 2×64821690² = 8403702988912200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 360031 + ... + 360210.

Almost surely, 2^64821690 is an apocalyptic number.

64821690 is an abundant number, since it is smaller than the sum of its proper divisors (103714938).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

64821690 is a wasteful number, since it uses less digits than its factorization.

64821690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 720254 (or 720251 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 64821690 is about 8051.1918372375. The cubic root of 64821690 is about 401.7045798670.

The spelling of 64821690 in words is "sixty-four million, eight hundred twenty-one thousand, six hundred ninety".