1621653977 has 4 divisors (see below), whose sum is σ = 1626300900. Its totient is φ = 1617007056.

The previous prime is 1621653961. The next prime is 1621653991. The reversal of 1621653977 is 7793561261.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 760877056 + 860776921 = 27584^2 + 29339^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621653977 - 2⁴ = 1621653961 is a prime.

It is a super-2 number, since 2×1621653977² = 5259523242239833058, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621653937) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2322938 + ... + 2323635.

It is an arithmetic number, because the mean of its divisors is an integer number (406575225).

Almost surely, 2^1621653977 is an apocalyptic number.

It is an amenable number.

1621653977 is a deficient number, since it is larger than the sum of its proper divisors (4646923).

1621653977 is an equidigital number, since it uses as much as digits as its factorization.

1621653977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4646922.

The product of its digits is 476280, while the sum is 47.

The square root of 1621653977 is about 40269.7650477377. The cubic root of 1621653977 is about 1174.8598539957.

The spelling of 1621653977 in words is "one billion, six hundred twenty-one million, six hundred fifty-three thousand, nine hundred seventy-seven".