1621106566 has 4 divisors (see below), whose sum is σ = 2431659852. Its totient is φ = 810553282.

The previous prime is 1621106561. The next prime is 1621106573. The reversal of 1621106566 is 6656011261.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6656011261 = 30703 ⋅216787.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621106561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 405276640 + ... + 405276643.

It is an arithmetic number, because the mean of its divisors is an integer number (607914963).

Almost surely, 2^1621106566 is an apocalyptic number.

1621106566 is a deficient number, since it is larger than the sum of its proper divisors (810553286).

1621106566 is an equidigital number, since it uses as much as digits as its factorization.

1621106566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 810553285.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 1621106566 is about 40262.9676750237. The cubic root of 1621106566 is about 1174.7276425630.

The spelling of 1621106566 in words is "one billion, six hundred twenty-one million, one hundred six thousand, five hundred sixty-six".